Surgical management of severe obesity in adolescents

INTRODUCTION — Severe obesity is a significant health problem facing a large proportion of adults and children in the United States and increasingly worldwide [1-3]. Due to a lack of nonsurgical options for severely obese adolescents and a demonstrated safety and efficacy record in adults, there has been increasing interest in surgical procedures for weight loss ("bariatric surgery") for selected adolescents with severe obesity. There is insufficient evidence bearing on safety or effectiveness to recommend use of surgery for children or preadolescents at this time.

The rationale, outcomes, and indications for weight loss surgery in adolescents will be reviewed here. The management and outcomes of weight loss surgery in adults and other aspects of obesity in children and adolescents are discussed separately:

●(See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

●(See "Bariatric surgery: Postoperative and long-term management".)

●(See "Clinical evaluation of the child or adolescent with obesity".)

●(See "Overview of the health consequences of obesity in children and adolescents".)

●(See "Prevention and management of childhood obesity in the primary care setting".)

RATIONALE — Children and adolescents with severe obesity are at risk for and are developing important comorbidities, including obstructive sleep apnea, diabetes, hypertension, dyslipidemia, nonalcoholic fatty liver disease, and idiopathic intracranial hypertension, as well as depression and impaired quality of life [4-9]. Severe obesity has also been linked to shorter life expectancy [10]; therefore, treatment that is targeted at obesity may reverse or prevent these problems and improve long-term health outcomes [11,12]. (See "Overview of the health consequences of obesity in children and adolescents".)

History of weight loss surgery — During the past 40 years, weight loss surgery has clearly been shown to produce significant and sustained reductions in body mass index (BMI), diabetes, and hypertriglyceridemia in adults. It also reduces mortality, as highlighted in a 24-year follow-up of patients undergoing Roux-en-Y gastric bypass (RYGB), adjustable gastric banding (AGB), or vertical banded gastroplasty in the Swedish Obese Subjects Study [13]. (See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

Bariatric surgery has also increasingly been used to treat adolescents with severe obesity, and the evidence base supporting use of surgery has accumulated, most notably over the past two decades. In late 2019, the Section on Obesity of the American Academy of Pediatrics (AAP) published a policy statement supporting the use of surgery within the context of a multidisciplinary program with pediatric expertise for treating youth with severe obesity [14]. In addition to providing clinical guidance, the policy statement highlighted concerns about access to care, which represents a barrier to the appropriate use of bariatric surgery among eligible adolescents. In 2023, the AAP published a clinical practice guideline that comprehensively addresses pediatric obesity treatment including recommendations for pharmacotherapy and referral for consideration of weight loss surgery [8].

Consequences of severe obesity — Obesity in children and adolescents is classified by severity, using the following thresholds (figure 1A-B):

●Class I – BMI ≥95^th percentile for age and sex or BMI ≥30 (whichever is lower).

●Class II – BMI ≥120 percent of the 95^th percentile values or a BMI ≥35 kg/m² (whichever is lower). This corresponds to approximately the 98^th percentile.

●Class III – BMI ≥140 percent of the 95^th percentile values or a BMI ≥40 kg/m².

Severe (class II or III) obesity affects approximately 10 percent of girls and 13 percent of boys 12 to 19 years old in the United States [15]. These children will almost always remain in the obese range as adults, and 65 percent will have class III obesity as adults (BMI ≥40 kg/m²) [16,17]. They have a significantly greater prevalence of cardiovascular risk factors compared with children with lesser degrees of obesity and will have more health complications and higher mortality compared with those who developed obesity during adulthood [18-22]. (See "Definition, epidemiology, and etiology of obesity in children and adolescents", section on 'Definitions' and "Overview of the health consequences of obesity in children and adolescents".)

Alternatives to surgery — Because of the potential risks of surgical weight loss, noninvasive approaches should always be the first-line treatment for any child or adolescent with obesity. The best established approaches are multidisciplinary, using family-based behavioral techniques to support changes in diet and physical activity, with goals of reducing caloric intake, improving the quality of the food intake, and increasing energy expenditure. Recommendations from the AAP and other professional organizations advocate early intervention with dietary and lifestyle changes for children with excessive weight gain.

Unfortunately, the limited data available suggest that dietary and behavioral interventions alone rarely achieve significant long-term success for individuals with severe obesity. As examples, adolescents treated with behavioral therapy (eg, those randomized to placebo with behavioral therapy as controls in pharmaceutical studies for weight loss) have typically demonstrated <3 percent weight loss [23,24]. Similarly, in a study from Sweden, the control group of adolescents with severe obesity experienced a 6 percent weight gain over five years of medical management; this is an informative finding given the 90 percent follow-up rate for this group [25].

An increasing number of drugs are available for the management of obesity in adolescents. Patient selection for pharmacotherapy, available drugs, and data on outcomes are discussed in a separate topic review. (See "Prevention and management of childhood obesity in the primary care setting", section on 'Pharmacotherapy'.)

TYPES OF SURGERY — The most widely performed procedures in adolescents and adults are the sleeve gastrectomy (SG; >80 percent) and Roux-en-Y gastric bypass (RYGB; <20 percent) [26-28]. Far fewer adjustable gastric banding (AGB; <5 percent) procedures are performed. Details of these procedures and the experience in adults are discussed in a separate topic review (see "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Procedures endorsed by the ASMBS'). Outcomes of these procedures and considerations specific to adolescents are discussed below. (See 'Outcomes' below and 'Postoperative management' below.)

Sleeve gastrectomy — The SG (also known as vertical sleeve gastrectomy) is a partial gastrectomy, in which the majority of the greater curvature of the stomach is removed, creating a tubular stomach (figure 2). The frequency of this procedure for weight loss surgery has been rapidly increasing, and it accounts for more than 80 percent of bariatric procedures in adolescents [27-31]. It is typically used as a standalone procedure [32]. If patients regain weight in the long term, the SG can be converted to a RYGB, but this is uncommon. Data on very long-term outcomes are pending. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Sleeve gastrectomy'.)

Because SG is less complex than RYGB and has a lower theoretical risk of micronutrient deficiencies, it is an appealing option for adolescents. In a study from the United States with five-year follow-up, SG was associated with reduced frequency of emergency department visits (53.3 versus 59.9 percent) and hospitalization (36.9 versus 52.1 percent) compared with RYGB [31]. There was no significant difference in the frequency of complications (1.5 versus 2.1 percent) or reoperations (7.2 versus 7.7 percent). Outcomes for weight loss and comorbidity improvement are generally excellent, although the long-term weight loss may be less than for RYGB, at least for a subset of patients [33]. Compared with AGB, SG has the advantage of avoiding a foreign body and potential associated complications. (See 'Outcomes' below.)

SG may be a particularly appropriate choice of procedure for individuals with cognitive deficits, younger age, or other issues that might increase risk for postoperative nutritional deficiencies. However, outcomes for these special populations remain unclear because the only information is from very small case series with several years follow-up. (See 'Special populations' below.)

Roux-en-Y gastric bypass — RYGB creates a small (less than 30 mL) proximal gastric pouch that is divided and separated from the distal stomach and anastomosed to a Roux-limb of small bowel 75 to 150 cm in length (figure 3). The surgery was the most commonly performed bariatric procedure in the United States until approximately 2012 but now accounts for less than 20 percent of procedures in adolescents. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Roux-en-Y gastric bypass'.)

The long-term outcomes for weight loss and comorbidity improvement are well established for RYGB, based on more than 25 years of experience with this procedure in adults. In addition, it has particularly dramatic benefits on glycemic control, which may offer some advantage for patients with type 2 diabetes [34]. On the other hand, there are probably more risks for nutritional deficiencies compared with SG. In particular, iron sufficiency and long-term outcomes for bone health after RYGB are not well studied. (See "Outcomes of bariatric surgery", section on 'Diabetes mellitus'.)

Adjustable gastric banding — AGB is a purely restrictive procedure that compartmentalizes the upper stomach by placing a tight, adjustable prosthetic band around the entrance to the stomach (figure 4). The US Food and Drug Administration (FDA) has approved two AGB devices for use in adults in the United States, but these devices are not FDA-approved for adolescents younger than age 18. With increasing use of SG, AGB use has dramatically declined. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Laparoscopic adjustable gastric banding'.)

Other — Endoscopically placed intragastric balloons are approved by the FDA for short-term use (up to six months) in adults with severe obesity but have only been studied in a few single-center, small case series of adolescents. In a two-year cohort study of 12 adolescents with severe obesity, clinically significant, modest improvements in weight (mean 5 percent loss) and some measures of glucose metabolism (insulin area under the curve and glycated hemoglobin) were seen at six months, while the intragastric balloon was in place [35]. However, after device removal, weight loss and cardiometabolic benefits were not sustained for most participants at two-year follow-up. Further, these devices are not approved for use in adolescents by the FDA. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Intragastric balloon'.)

In the past, the range of surgical weight loss procedures performed on adults and a few adolescents included jejunoileal bypass (a procedure associated with a high rate of malabsorptive complications), vertical banded gastroplasty, and banded gastric bypass. Due to unsatisfactory safety profiles and/or efficacy, these procedures are no longer recommended. Other procedures that cause malabsorption, such as biliopancreatic diversion, are occasionally performed on adults but are generally not recommended for adolescents, due to lack of safety data in this age group and concerns about long-term nutritional complications [36]. (See "Bariatric procedures for the management of severe obesity: Descriptions".)

MECHANISMS OF WEIGHT LOSS — Reduction of caloric intake plays an important role in the dramatic weight loss produced by bariatric surgery. However, this is only partially attributable to a reduced capacity of the stomach or pouch. Many patients report a subjective decrease in appetite and increase in postprandial satiety after surgery, which help them maintain lower intakes of food. This experience suggests that the effects of bariatric surgery on weight loss and comorbidities may have neuroendocrine mechanisms and are not entirely attributable to mechanical restriction of food intake or to malabsorption.

Emerging data suggest that alterations in neuroenteric hormones that regulate appetite and energy expenditure could contribute to changes in satiety after surgery. Several studies have demonstrated an increase in postprandial peptide YY (PYY) concentrations after Roux-en-Y gastric bypass (RYGB) compared with lean or obese nonoperative controls [37,38]. This postprandial increase in PYY is not reported after an adjustable gastric banding (AGB) [39,40]. However, a single series of 12 patients undergoing the vertical banded gastroplasty (also purely restrictive) reported an increase in fasting and postprandial PYY concentrations after surgery to levels comparable with concentrations measured in lean controls [41].

In addition, bile acid signaling, mediated through the farnesoid X receptor (FXR), appears to be integral to achieving the weight loss and beneficial metabolic effects of sleeve gastrectomy (SG) in rodent models of bariatric surgery [42]. Studies in adults have also demonstrated a rise in circulating total bile acids after RYGB and to a lesser degree after SG; however, no significant change was demonstrated after AGB [43,44]. Bile acids have also been shown to rise significantly in adolescents as well during the rapid weight loss phase in the first three months after SG [45].

PREOPERATIVE EVALUATION AND SCREENING

Screening — Recommended screening prior to surgical weight loss procedures includes evaluation for the presence and severity of coexisting diseases, as well as assessment of the patient's and family's understanding and readiness for a life-changing and often permanent procedure. Recommended screening tests and evaluations that should be completed during the evaluation are highlighted in the table (table 1). The final decision on whether to proceed with surgery must be made by the multidisciplinary team, taking into consideration both objective and subjective assessments of the patient's severity of obesity and related diseases, risk of future health problems, failure to lose weight through more conventional means, psychosocial status and support, and patient and family readiness for surgery.

A multidisciplinary approach is recommended when offering weight loss surgery to adolescents [46-48]. At a minimum, the team evaluating and caring for the candidate should include an experienced bariatric surgeon, pediatric obesity specialist, nurse, dietician, and pediatric psychologist or psychiatrist. One of these providers or an additional team member should have responsibility for coordinating each patient's care and ensuring follow-up and adherence to the prescribed medical regimen. The program also must have ready access to relevant pediatric subspecialties, including endocrinology, cardiology, gastroenterology, pulmonology, gynecology, and orthopedics, for further evaluation and/or management of specific comorbidities as needed.

Patient selection — For adolescents younger than 18 years of age, the following thresholds are recommended for consideration of weight loss surgery; these reflect percentile-based definitions for severe obesity in youth (figure 1A-B) [6,8,14,49,50] (see "Definition, epidemiology, and etiology of obesity in children and adolescents", section on 'Definitions'):

●Class II obesity (BMI ≥120 percent of the 95^th percentile for BMI for age or BMI ≥35 kg/m², whichever is lower), with a comorbidity of obesity that has significant effects on health, including but not limited to type 2 diabetes mellitus, idiopathic intracranial hypertension, obstructive sleep apnea (apnea-hypopnea index >5), nonalcoholic steatohepatitis, Blount disease, slipped capital femoral epiphysis, gastroesophageal reflux disease, arterial hypertension, insulin resistance, or reduced health-related quality of life

or

●Class III obesity (BMI ≥140 percent of the 95^th percentile of BMI for age or BMI ≥40 kg/m², whichever is lower), with or without an obesity-related comorbidity

In adults, the threshold for consideration of weight loss surgery is a body mass index (BMI) ≥35 kg/m²; a threshold of ≥30 kg/m² is used for individuals with significant current comorbidities, such as diabetes [51]. (See "Bariatric surgery for management of obesity: Indications and preoperative preparation".)

Current guidelines for adolescent bariatric surgery do not recommend limiting access to surgery based on pubertal status or physical maturity, as determined by Tanner stage or bone age. Initially, it was theorized that rapid weight loss might inhibit linear growth; however, this has not been demonstrated. On the contrary, a small study of sleeve gastrectomy (SG) in children younger than 14 years found improved linear growth postoperatively compared with matched controls [52]. (See 'Special populations' below.)

Regarding a history of efforts to lose weight through changes in diet and physical activity, there is no evidence that prolonged preoperative weight management programs enhance selection of patients for weight loss surgery. However, consistent attendance in such a treatment program may be a valuable indicator of the patient's ability to understand and adhere to medical and nutritional recommendations postoperatively.

These guidelines rest primarily on expert opinion and retrospectively evaluated outcomes data [6]. There is only one randomized controlled trial in adolescents that demonstrates superiority of surgical weight loss (in this case, adjustable gastric banding) compared with conventional medical therapy for the severe comorbidities listed above [53,54]. However, randomized controlled trials in adults with type 2 diabetes mellitus have demonstrated that bariatric surgery (including Roux-en-Y gastric bypass [RYGB], adjustable gastric banding [AGB], and SG) is significantly more effective than conventional or intensive medical therapy in resolution of type 2 diabetes mellitus at one and two years postoperatively [55,56].

It should be recognized that the above criteria alone are not sufficient to select the patients who are most likely to benefit from weight loss surgery during adolescence. We recommend that the multidisciplinary team consider carefully whether the patient and family have the ability and motivation to adhere to recommended treatments pre- and postoperatively, including consistent use of micronutrient supplements. Evidence may include a history of reliable attendance at office visits for weight management and adherence to other medical guidance. In addition, the team should consider whether the adolescent shows evidence of mature decision-making, with appropriate understanding of the risks and benefits of surgery, and has support but not coercion from family members.

Although no studies have directly addressed the timing of surgical intervention relative to BMI trends or age (see 'Weight loss' below), many experts believe that earlier surgical intervention probably is beneficial for adolescents with progressively worsening obesity (analogous to the surgical approach for cancers). This opinion is based upon indirect evidence from observational studies in adolescents and adults in which lower BMI at baseline generally predicts lower absolute BMI after surgery. Because bariatric surgery results in a loss of 25 to 30 percent of BMI, on average, treatment rendered earlier after the diagnosis of severe obesity is more likely to result in postoperative BMI values that are in the healthier ranges [57]. A study that followed adolescents for five years after weight loss surgery found no difference in weight loss or quality of life in younger patients (13 to 15 years, n = 66) compared with older patients (16 to 19 years, n = 162) [58]. This suggests that intervention at a younger age is effective and that outcomes are more likely mediated by BMI rather than age.

Regarding comorbidity resolution, there is also compelling evidence that intervening during adolescence, rather than waiting until adulthood, increases the likelihood of remission of cardiovascular risk factors and diabetes, which are known to have a more aggressive course in adolescent patients [34,59-62].

Contraindications for surgical weight loss procedures in adolescents include:

●Medically correctable cause of obesity

●An ongoing substance abuse problem (within the preceding year)

●A medical, psychiatric, psychosocial, or cognitive condition that prevents adherence to postoperative dietary and medication regimens or impairs decisional capacity

●Current or planned pregnancy within 12 to 18 months of the procedure

●Inability on the part of the patient or parent/guardian to comprehend the risks and benefits of the surgical procedure

Special populations — The appropriate use of weight loss surgery for individuals with cognitive deficits or immaturity remains unclear. There is limited evidence that weight loss surgery, and SG in particular, may be safe and beneficial in patients with cognitive deficits, younger age, or other issues. Outcomes of SG for these populations are based on small case series with several years of follow-up.

●Syndromic obesity and/or intellectual disability – In two small case series, adolescents with intellectual disability (but not Prader-Willi syndrome) had similar weight outcomes after SG compared with those without intellectual disability [63,64]. Similarly, two overlapping case series of 226 pediatric patients undergoing SG included seven patients with Prader-Willi syndrome, two with Bardet-Biedl syndrome, three with intellectual disability, and one with Down syndrome [65,66]. There were no deaths and no major complications.

One contemporary study reports benefits of a narrow SG for individuals with Prader-Willi syndrome, most with two to five years of follow-up [67]. However, more investigation is required before use of weight loss surgery for patients with Prader-Willi or other syndromes can be widely recommended [68,69]. In particular, it is unclear whether long-term durability of weight loss after SG in individuals with Prader-Willi syndrome will be achieved, and the type and frequency of adverse events is inadequately explored. (See "Prader-Willi syndrome: Management".)

●Preadolescent children – Outcomes of surgery in preadolescent children were reported in a study on a population that included 19 children ages 5 through 8.99 years and 56 children 9 to 12.99 years [52]. Children in both age groups experienced good linear growth during the first few years after weight loss surgery. In addition, the two overlapping case series described above included 74 prepubertal patients (5 to 12.99 years), including eight with intellectual disability [65,66]. However, the data collection and follow-up are insufficient to determine the safety and outcomes of SG in this younger age group.

●Hypothalamic obesity – Hypothalamic obesity is particularly resistant to medical and lifestyle management, and weight control may be further complicated by the necessary hormone replacement. Emerging evidence supports bariatric surgery as a means to achieve meaningful weight loss for this population. A review of data from a hypothalamic obesity registry found that bariatric surgery was superior (median BMI decrease of -8.2 kg/m²) compared with lifestyle (median BMI -3.4 kg/m²) or pharmacologic (median -2.3 kg/m²) interventions [70].

Retrospective observational studies have noted initial weight loss with AGB, SG, and RYGB procedures in this population; however, RYGB may have more significant and durable weight loss. One study compared long-term weight loss (median two to five years) after SG and RYGB and found that weight loss was superior after RYGB and was comparable with postoperative weight loss in control patients without hypothalamic obesity [71,72]. In a meta-analysis of 21 cases of surgical management for hypothalamic obesity, mean weight loss was -20.9 kg after six months (95% CI -35.4 to -6.3) and -15.1 kg after 12 months (95% CI -31.7 to +1.4) [73]. This meta-analysis also demonstrated superior weight loss with RYGB, with a mean weight loss of -31.0 kg (95% CI -77.5 to +15.5) and -33.7 kg (95% CI -80.7 to +13.3) after 6 and 12 months, respectively.

PERIOPERATIVE SAFETY — To provide for optimum safety of the patient while hospitalized, it is important to ensure that the program also has access to pediatric anesthesiology and radiology consultants who have experience caring for individuals with severe obesity. Specialized equipment, such as computed tomography (CT), magnetic resonance imaging (MRI), and dual-energy x-ray absorptiometry (DXA) scanners, often have weight limitations, which may preclude their use for these patients [74]. Further, basic equipment such as operating tables, stretchers, scales, beds, and toilets that can support extreme weight ranges must be available to ensure safety of the patient and caretakers.

To prevent the development of venous thromboembolism, we recommend frequent ambulation, starting on postoperative day 0, and the use of compression boots when the patient is not ambulatory. Mechanical and chemoprophylaxis are routinely recommended in the adult guidelines [75]. No formal recommendations exist in the adolescent bariatric population; thus, adoption of adult guidelines for adolescents for chemoprophylaxis with low-molecular weight heparin in the perioperative period is reasonable. (See "Bariatric surgery: Postoperative and long-term management", section on 'Venous thromboembolism' and "Bariatric operations: Early (fewer than 30 days) morbidity and mortality", section on 'Venous thromboembolism'.)

Weight loss surgery frequently leads to an abrupt resolution of hypertension and hyperglycemia. Antihypertensive or hypoglycemic medications that were given preoperatively usually can be discontinued after surgery, and the patient should be monitored for his or her response. (See "Bariatric surgery: Postoperative nutritional management", section on 'Diet and texture progression' and "Bariatric surgery: Postoperative and long-term management".)

POSTOPERATIVE MANAGEMENT — Average inpatient stays range from one to three days for laparoscopic Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) [76,77]. Postoperative management for patients includes strict measurement of intake and output and gradual advancement of diet from nil per os (NPO) to clear liquids to a high-protein liquid diet. (See "Bariatric surgery: Postoperative nutritional management" and "Bariatric surgery: Postoperative and long-term management", section on 'Postoperative care after discharge'.)

Diet — Dietary management after discharge varies with the type of surgery. After RYGB and SG, the patient advances through several stages, from high-protein shakes to gradual introduction of greater volumes and more textured and solid foods [78]. The advancement to regular foods is slow, occurring over the first six months after surgery. For best results, the patient is encouraged to eat three to four small, high-protein meals per day and to avoid high-fat and -carbohydrate foods as these may provoke malabsorptive or dumping side effects. Supplemental fluids are encouraged to avoid dehydration (64 to 92 ounces per day of sugar-free, noncarbonated beverages). Drinks should be sugar-free to avoid dumping syndrome and weight regain through overconsumption of liquid calories. Patients also are advised to avoid drinking during meals to avoid nausea and vomiting. Some patients experience greater degrees of nausea in the first postoperative month after SG as compared with RYGB, requiring addition of antiemetics and antinausea medications. Typically, however, this resolves over time.

Follow-up visits are typically performed at two weeks postoperatively, then 1, 3, 6, 9, and 12 months after surgery. After that, annual follow-up is recommended for monitoring of anthropometric measurements, nutritional status, residual comorbidities, and general health. Follow-up for adjustable gastric banding (AGB) patients typically is more frequent due to the need for band adjustments. Some patients require visits every four to six weeks during the first one to two years.

General recommendations for long-term weight maintenance include:

●Drinking 8 to 12 8 ounce servings of sugar-free liquids per day. Some providers encourage the patient to avoid or limit caffeinated or carbonated beverages, based on theoretical concerns that these substances may be detrimental after surgery, although there is little evidence to support this concern.

●Exercising 30 to 60 minutes daily.

●Eating protein first at each meal (1 g/kg of ideal body weight).

●Three to four portion-controlled meals per day, with minimal snacking between meals.

●Taking daily vitamin and mineral supplementation.

These guidelines may need to be tailored to meet an individual patient's needs if significant weight regain or too much weight loss has occurred.

Nutritional supplements — After RYGB or SG procedures, lifelong supplementation with vitamins and minerals is recommended to avoid development of nutritional complications secondary to reduced intake and/or mild malabsorption [14]. Although SG and AGB may be associated with reduced risk for nutritional deficiencies compared with RYGB, long-term data on nutritional outcomes are still lacking. Therefore, the same supplementation is prescribed for all patients regardless of the bariatric procedure. As long-term data on outcomes in adolescents are collected, these initial recommendations may be modified.

After RYGB, patients should conscientiously adhere to a supplementation regimen because of risks for malabsorption of micronutrients; the recommended doses and preparations vary somewhat among practices and may be adjusted based on laboratory measures.

We prescribe the following supplements for all patients (table 2):

●Standard multivitamin with folate and iron, or prenatal vitamin if female (once or twice daily).

●Vitamin B12, 500 micrograms sublingually daily, or 1000 micrograms intramuscularly monthly [78]. In those with satisfactory levels at annual monitoring, a single semiannual dose of 3000 micrograms intramuscularly can be considered.

●Calcium, 1200 to 1500 mg daily (measured as elemental calcium), with 800 to 1000 international units of vitamin D.

Additional supplementation may be necessary during pregnancy or as indicated by laboratory testing. If postoperative vomiting is severe, vitamin B1 (thiamine) deficiency also can rapidly develop [79]. Vitamin B1 deficiency is particularly important to recognize early as lasting neurologic sequelae can result if rapid replenishment of vitamin B1 is not initiated [80,81]. In the author's program, vitamin B1 supplementation (50 mg orally daily) is provided during the first six months after surgery as a prophylactic measure.

Nutritional monitoring — After bariatric surgery, lifelong monitoring of nutritional status is recommended. The following parameters are measured annually:

●Complete blood cell count with differential.

●Serum iron and ferritin.

●Red blood cell folate, serum vitamin B12, and serum homocysteine.

●Serum thiamine (vitamin B1).

●Hepatic panel, including albumin, total protein, serum aminotransferase levels, gamma-glutamyl transpeptidase, and alkaline phosphatase.

●Calcium, 25-hydroxyvitamin D, and parathyroid hormone.

●Dual-energy x-ray absorptiometry (DXA) scan to monitor lean and fat-free mass and bone density. This test is optional and may not be needed annually for patients with good nutritional status.

Adjustments in nutritional supplements may need to be made if specific deficiencies emerge over time, particularly because many adolescents may be nonadherent or only partially adherent to recommended supplementation. (See "Bariatric surgery: Postoperative nutritional management", section on 'Postsurgical screening'.)

In addition, monitoring of postoperative eating behaviors appears to be important. In a sample of 234 adolescents undergoing bariatric surgery, loss-of-control eating was reported by up to 28 percent preoperatively and by significantly fewer (<15 percent) postoperatively [82]. While preoperative loss-of-control eating was not associated with postoperative weight loss outcomes, emergence of loss-of-control eating behaviors at one, two, and three years postoperatively was associated with declines in weight loss efficacy. These findings suggest that loss-of-control eating behaviors could be a modifiable target to preserve early weight loss effects of after bariatric surgery.

Pregnancy prevention — Severe obesity can lead to irregular menstruation, anovulation, and infertility. Conversely, surgically induced weight loss leads to resumption of ovulation and renewed fertility for some women [83,84]. In a series of 47 adolescent females who had undergone bariatric surgery during adolescence, a higher-than-expected rate of pregnancy was observed (seven pregnancies, six of which occurred between 10 and 22 months postoperatively) [85]. Although the medical and psychosocial factors contributing to this high rate could not be addressed in this retrospective report, the high rate of pregnancy highlights the importance of addressing contraception and pregnancy prevention in all female adolescents undergoing bariatric surgery.

Pregnancy should absolutely be avoided for at least 12 to 18 months after surgery due to the rapid weight loss and potential micronutrient deficiencies, which may have adverse effects on the mother and fetus. However, long-term effects of bariatric surgery on fertility and pregnancy outcomes are generally good. (See "Fertility and pregnancy after bariatric surgery".)

The efficacy of oral contraceptives or transdermal contraceptive patches may be compromised in patients with obesity [86-88]. This is a significant concern both pre- and postoperatively as many adolescent patients may still have a postoperative body mass index (BMI) >30 kg/m² despite significant weight loss after surgery. The American College of Obstetricians and Gynecologists recommends using nonoral forms of hormonal contraception in women who have undergone malabsorptive bariatric surgery and desire hormonal contraception. Further, use of oral contraception is associated with an increased risk of thromboembolism, which may compound the higher risk associated with obesity.

Depot medroxyprogesterone acetate is effective in overweight or obese women but has been reported to cause significant weight gain (mean of 4 to 9 kg) in overweight or obese adolescents [89,90]. In contrast, the levonorgestrel intrauterine system (Mirena) does not cause weight gain and remains effective in overweight/obese women [91]. It has several notable advantages that make it an optimal choice for adolescent females after bariatric surgery, including five-year efficacy, promotion of amenorrhea (which could help reduce risk of iron deficiency anemia after surgery), and option for placement at time of bariatric surgery [92]. However, as with all forms of hormonal contraception, adolescents should be counseled to use additional barrier protection against sexually transmitted diseases. These and other considerations about contraceptive choice are discussed separately. (See "Fertility and pregnancy after bariatric surgery".)

Adolescent females who become pregnant after weight loss surgery should be counseled about adequate macro- and micronutrient intake. At a minimum, a prenatal vitamin with folic acid and iron, 1200 to 1500 mg of calcium citrate with 800 international units vitamin D, and 500 mcg of oral vitamin B12 daily should be prescribed [93]. Additional iron supplementation may be necessary in pregnant women after RYGB. Iron, folate, and vitamin B12 levels should be monitored during pregnancy and additional supplementation prescribed as indicated by results. Protein intake of at least 1 g/kg of ideal body weight (typically 60 to 80 g) per day is recommended.

Other risks — Adolescents undergoing bariatric surgical treatment may also be at increased risk for psychosocial challenges including suicide and substance abuse disorders. While a prior history of psychopathology does not appear to impact the efficacy of weight loss [94], those with preexisting mental health problems should be considered an at-risk group and may have more difficulties with compliance with postoperative treatment recommendations and, thus, may benefit from more frequent clinical monitoring and anticipatory guidance.

Regarding suicide in particular, adult bariatric patients appear to have higher rates of suicidal thoughts and behaviors [95] (see "Outcomes of bariatric surgery", section on 'Psychosocial impact'). Very few studies have explored suicidal behaviors in adolescents undergoing bariatric surgery, but at the time of preoperative assessment, a prior history of suicidal ideation or attempt was reported in 40 and 15 percent, respectively [96]. Following gastric bypass, 14 percent of adolescents participating in a Swedish study reported suicidal ideation at two years postoperatively [97]. In the Teen-LABS study (Longitudinal Assessment of Bariatric Surgery), 16 percent of participants reported suicidal thoughts and behaviors (STB) after surgery, compared with 18 percent in a group of severely obese adolescents who did not undergo surgical weight loss [98]. Predictors or correlates of postoperative STBs were related to prior psychopathology, victimization, and drug/alcohol use and not to surgery-specific factors such as magnitude of weight loss or weight loss satisfaction. Suicide risk reduction is a public health priority for adolescents and young adults. While use of bariatric surgery in adolescence does not appear to increase (or lessen) the risk of engaging in post-surgery STBs, these risks are found in a subgroup of adolescents with poorer psychosocial health. Adolescents with a history of depression and/or past history of suicidal behaviors should be followed closely.

Experimentation with alcohol and illicit substances is common in adolescents, with almost one-half of students reporting experience with use of an illicit substance by the 12^th grade [99]. Regarding alcohol and substance use, adolescents undergoing bariatric surgery report lower rates of consumption than national base rates [100]. Nevertheless, the impact of altered anatomy and metabolism on elevating blood concentrations of alcohol after ingestion in a population at risk for substance use suggests that this is an important area for future research and clinical monitoring. (See "Identification and management of unhealthy alcohol use in the perioperative period", section on 'Epidemiology'.)

Comorbidity reassessment — Annual monitoring of cardiometabolic outcomes is recommended by obtaining the following labs and reassessing for recurrent or ongoing symptoms of sleep apnea or other preexisting comorbid conditions.

●Lipid panel

●Hemoglobin A1c

●Hepatic panel

●Cystatin C, creatinine

●Erythrocyte sedimentation rate

OUTCOMES

Weight loss — Both sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) in adolescents lead to clinically important decreases in weight and body mass index (BMI) in the majority of patients in the short to intermediate term (one to three years postoperatively). Information about long-term outcomes (longer than three years) is more limited, but the weight loss appears to be sustained, though attrition over time could bias findings.

The largest prospective study of outcomes of weight loss surgery in adolescents included 242 adolescents with severe obesity who predominantly underwent SG or RYGB at five centers in the United States with special expertise in bariatric surgery for this age group (Teen-LABS study) [101]. The mean age of the participants was 17±1.6 years, and one-third were between 13 and 15 years of age. Among 67 participants undergoing SG, BMI decreased from 50 kg/m² at baseline to 37 kg/m2 (a 26 percent reduction) three years postoperatively. Among 161 participants undergoing RYGB, BMI decreased from 54 kg/m² at baseline to 39 kg/m² (a 28 percent reduction) three years postoperatively (figure 5). At three years, weight regain to above baseline occurred in only 4 percent of participants with SG and 2 percent of those with RYGB.

Longer-term outcomes were reported in a population from one of the Teen-LABS centers, which reported outcomes for 58 individuals undergoing RYGB with more than five years follow-up (FABS-5+ study) [57]. At mean follow-up of eight years, BMI had decreased from 58.5 to 41.7 kg/m², representing a 29.2 percent decrease from baseline but a modest increase from the average nadir BMI one year postoperatively. At long-term follow-up, 63 percent had at least moderately severe obesity (BMI ≥35 kg/m²). A separate study from Sweden described long-term outcomes after RYGB in a group of 81 adolescents with less severe obesity [25]. Prior to surgery, the mean BMI was 45.5 kg/m²; at follow-up five years postoperatively, the mean BMI was 32.3 kg/m² and 28 percent had BMI ≥35 kg/m². In a small randomized trial (50 participants age 13 to 16 years, mean BMI 42.6 kg/m² at baseline), RYGB or SG was substantially more effective over two years compared with intensive nonsurgical therapy (difference in mean BMI -12.4 kg/m² [95% CI -15.5 to -9.3]) [102]. Together, these studies suggest that surgical intervention in patients with moderate obesity has better absolute BMI outcomes than for patients with severe obesity, supporting the notion that early intervention may be beneficial.

Previous studies reporting outcomes of weight loss surgery in adolescents have utilized a retrospective design and report short- to intermediate-term outcomes (outcomes measured from 1 to 6.3 years after surgery). A few studies have reported small numbers of patients 10 or more years after their procedure. In most of these long-term studies, a substantial number of subjects were lost to follow-up, which could bias findings.

Despite these limitations, these studies confirm that clinically significant and durable weight loss can be achieved in most patients by either SG [65,66,103] or RYGB [104-108], while adjustable gastric banding (AGB) is probably somewhat less effective, with slower and less weight loss [53,108-115]. As an example, a meta-analysis of 37 studies reported substantial weight loss with any of these procedures. Mean BMI loss was 16.6 kg/m² for RYGB, 14.1 kg/m² for SG, and 11.6 kg/m² for AGB; these differences were not statistically significant, and comparison of outcomes was limited by lack of randomization among the procedures and different lengths of follow-up [33]. A subsequent analysis of adolescents undergoing bariatric procedures at health systems affiliated with 11 clinical data research networks in the United States from 2005 to 2015 confirmed these estimates. The cohort included a total of 544 individuals undergoing bariatric surgery (306 SG, 177 RYGB, and 61 AGB) [29]. SG represented only 13 percent of cases from 2005 to 2009 and increased to 83 percent of cases from 2014 to 2015. At one year postoperatively, estimated mean BMI changes were -31 percent for RYGB, -28 percent for SG, and -10 percent for AGB. By three years postoperatively, estimated mean BMI changes were -29 percent for RYGB and -25 percent for SG. Thus, in this study, adolescents undergoing RYGB and SG experienced similar declines in BMI, while AGB was significantly less effective.

Of note, the nadir postoperative BMI tends to be lower in patients with less severe obesity preoperatively as compared with those with more severe obesity, although the percent BMI change is similar [116]. In a large series of patients from a single center undergoing RYGB, the mean nadir postoperative BMI was 31, 38, and 47 kg/m² for patients with starting BMIs between 40 to 54, 55 to 65, and >65 kg/m², respectively [117].

It is not clear to what degree weight loss will be sustained in adolescents and whether comorbid conditions will recur if significant weight is regained in long-term follow-up. Two studies with 4 to 10 years of follow-up suggest that 10 to 15 percent of patients regain significant weight after RYGB procedures [104,118]. Specific predictors of weight regain after surgical weight loss procedures are unknown for adults and adolescents. Some long-term retrospective studies and meta-analyses have suggested a weight loss advantage comparing RYGB with SG; however, there is still insufficient information to directly compare the long-term weight loss outcomes of SG with those for RYGB or AGB in adolescents [29,33,115,119-122].

Comorbidity improvement — Weight loss surgery results in resolution of or improvement in most obesity-related diseases in both adults and adolescents. The most dramatic improvements have been seen in insulin resistance, triglyceride levels, type 2 diabetes, elevated blood pressure, obstructive sleep apnea, nonalcoholic fatty liver disease, renal function, male hypogonadism, as well as depression and quality of life [34,57,109,113,123-133].

●Metabolic and cardiovascular outcomes – In the Teen-LABS study described above, type 2 diabetes resolved by three years postoperatively in 95 percent of the participants who had the condition at baseline and other comorbidities also resolved in most patients, including prediabetes, elevated blood pressure, and dyslipidemia (figure 6) [101,132]. Cardiovascular risk factor resolution was associated with increased weight loss, female sex, and younger age at the time of bariatric surgery [132]. Similar improvements were seen in two studies with more than five-year outcomes, demonstrating long-term durability of these important metabolic effects of surgery [25,57]. The metabolic improvements are consistent with the observation that weight loss after surgery is accompanied by a significant reduction in body fat (from 51 to 37 percent in one series) with relative preservation of lean body mass [134]. Another study showed improvements in obesity-associated cardiac abnormalities, including concentric left ventricular hypertrophy and diastolic function, as measured by echocardiogram performed before and approximately 10 months after RYGB surgery [135].

Outcomes of RYGB in adolescents (n = 161) were directly compared with those of adults (n = 396) in a secondary analysis of data from two large National Institutes of Health-funded consortia [136]. There were no significant differences between adolescents and adults in percent weight loss at five years (-26 versus -29 percent, respectively; p = 0.08). However, after surgery, adolescents were significantly more likely than adults to experience remission of type 2 diabetes (86 versus 53 percent; risk ratio [RR] 1.27, 95% CI 1.03-1.57) and remission of hypertension (68 versus 41 percent; RR 1.51, 95% CI 1.21-1.88).

●Renal function – Another Teen-LABS analysis highlighted kidney function, a seldom reported outcome after bariatric surgery. Among severely obese adolescents with impaired kidney function at baseline (estimated glomerular filtration rate [eGFR] <90 mL/min/1.73 m²), mean eGFR improved from 76 mL/min/1.73 m² to 102 mL/min/1.73 m² at three years follow-up (p<0.0001) [137]. Similarly, participants with evidence of kidney injury (albuminuria) at baseline demonstrated a significant improvement of albumin-to-creatinine ratio (ACR); geometric mean of ACR was 74 mg/g at baseline and decreased to 17 mg/g at three years (p<0.0001). Those with normal renal function and no albuminuria at baseline remained stable throughout the study period.

●Functional mobility – In the Teen-LABS cohort evaluated three years postoperatively, there were substantial improvements in functional mobility, as demonstrated by a 400-meter walk test, and in musculoskeletal pain [138,139].

●Psychosocial outcomes – Bariatric surgery leads to improvements in psychosocial functioning, but the improvements are often transient. In the Teen-LABS study, quality of life improved substantially after weight loss surgery [101,139]. A study of 37 adolescents undergoing RYGB showed that anxiety and depression symptoms were higher at baseline than sex-specific norms but declined significantly by four months after surgery [140]. There was no change in anger and disruptive behavior symptoms. In another study of 16 adolescents undergoing RYGB, a substantial reduction in depressive symptoms occurred over the first postoperative year, accompanied by improvements in measures of health-related quality of life and self-concept (social, appearance, and close friendship) [141]. However, these improvements decelerated in the second postoperative year, accompanied by modest weight regain and slight increase in depressive symptoms, as well as declines in measures of health related to quality of life, including social, body esteem, physical comfort, and total domains, as well as self-concept. At two years postoperatively, approximately one-half of the patients with baseline psychopathology continued to experience symptoms [142]. These observations underscore the importance of long-term psychosocial monitoring after surgery. (See 'Other risks' above.)

Short-term complications — Short-term complications (<30 days after surgery) are generally similar to those in adults and occur in 6 to 8 percent of individuals [27,143]. Complications after RYGB include intestinal leakage at anastomotic sites, wound infections, pulmonary embolus, gastrojejunal strictures requiring endoscopic dilatation, small bowel obstruction, gastrogastric fistula formation, and symptomatic cholelithiasis [105]. Complications of SG also include leak at the staple line. SG patients also may experience heightened and more protracted nausea in the first month postoperatively compared with patients undergoing RYGB. Complications of AGB procedures in adolescents and adults include band slippage requiring repositioning, gastric obstruction, and esophageal or gastric pouch dilatation [111].

Among the 242 participants in the Teen-LABS study cited above, there were 20 major complications within 30 days of surgery (8 percent overall; RYGB 9 percent, SG 5 percent, and AGB 7 percent) [27]. Major complications included reoperation for bowel obstruction/bleeding leak or sepsis, postoperative bleeding requiring transfusion, or intraoperative splenic injury. There were 47 minor complications (15 percent overall; RYGB 17 percent, SG 12 percent, and AGB 7 percent). Most major and minor complications occurred prior to discharge from the hospital, and there were no deaths. Similarly, reports from other registries indicate that short-term complications appear to be somewhat lower for patients undergoing SG as compared with those undergoing RYGB [30]. Although AGB appears to offer a short-term advantage in complication rates, the procedure also is associated with greater long-term risks for revisional surgery, as described below. (See 'Long-term complications' below.)

Several studies performed in the United States suggest weight loss surgery may be somewhat safer in adolescents as compared with adults [36]. The reason for this is unknown, but the observation may reflect a better state of health among individuals undergoing surgery at a young age.

●A national analysis of weight loss surgery using utilization codes revealed no perioperative mortality and a significantly shorter length of stay in adolescents as compared with adults [144]. Five percent of adolescent patients had major complications, but the majority (78.3 percent) were respiratory in nature.

●A large study comparing the perioperative outcomes of weight loss surgery between 309 adolescents and 55,192 adults (>18 years) found that the overall 30-day complication rate was significantly lower in adolescents (5.5 percent) as compared with adults (9.8 percent). There was no difference in observed:expected mortality ratios. The 30-day morbidity and mortality rates for adolescents following restrictive procedures (AGB and vertical banded gastroplasty) were nil, compared with the morbidity rate of 4.3 percent for laparoscopic RYGB and 7.6 percent for open RYGB [145].

Long-term complications

Nutritional complications — Long-term complications of weight loss surgery in adolescents are primarily nutritional. In particular, patients are at risk for deficiencies of iron, vitamin B12, vitamin D, and thiamine (vitamin B1). These risks are generally higher for RYBG compared with SG. This was shown in five-year outcomes for the Teen-LABS study [146]:

●Iron deficiency – Prevalence of low serum ferritin increased (71 percent for RYGB; 45 percent for SG).

●Vitamin B12 – Prevalence of low vitamin B12 concentrations increased to approximately 12 percent after either procedure.

●Vitamin D and parathyroid hormone – Approximately 40 percent of participants had suboptimal serum 25-hydroxyvitamin D concentrations (<20 ng/mL) at baseline, with no significant change during postoperative follow-up. However, parathyroid hormone concentrations significantly increased during follow-up and the risk of abnormal parathyroid hormone was nearly sixfold higher after RYGB compared with SG. Elevated parathyroid hormone is a marker for functional vitamin D deficiency and raises concern about long-term bone health.

●Thiamine – Functional thiamine status (erythrocyte transketolase activity) was normal for most patients throughout this study. However, multiple case reports describe acute symptomatic thiamine deficiency in some patients after RYGB [79,80].

The risk for these deficiencies decreased with adherence to micronutrient supplements and increased with pregnancy [146]. These findings extend those from earlier studies of an overlapping cohort [57,101] and confirm the increased risk for RYGB compared with SG.

Because these nutritional deficiencies are common after weight loss surgery, lifelong vitamin and mineral supplementation is imperative. However, adherence to supplementation regimens among adolescents may be poor; one study reported that only 13 percent of adolescents were adherent to all prescribed nutritional supplementation [104,118]. The specific recommendations are outlined above. (See 'Nutritional supplements' above.)

RYGB is associated with reduced bone mass and increased fracture risk in adults and is probably caused by a combination of reduced mechanical load, changes in adipogenic hormones, and nutritional deficiencies [147,148]. In adolescents, reduced bone mass has been noted two years after weight loss surgery but remains appropriate for the individual's age and new body weight [149-151]. However, a study that used advanced quantitative bone imaging in young adults undergoing sleeve gastrectomy found decreased bone strength and increased bone marrow adipose tissue in the lumbar spine two years later [152]. Long-term studies are few, and the clinical implications of these changes are unclear. However, these findings underscore the importance of measures to optimize bone health after weight loss surgery, including supplementing and monitoring vitamin D and calcium and encouraging weight-bearing exercise [153]. (See 'Nutritional supplements' above and 'Nutritional monitoring' above.)

Other complications

●Postprandial hypoglycemia – Recurrent episodes of severe postprandial hypoglycemia may develop after RYGB and SG in some adult patients [154-156]. The mechanism of these hypoglycemic episodes is not known but may result in part from increased incretin secretion after surgery, pancreatic islet cell hyperplasia, and inappropriate postprandial hyperinsulinemia [157,158]. Although a similar syndrome in adolescents after RYGB has not yet been reported in the literature, at least one adolescent patient in the authors' weight loss surgery program developed severe postprandial hyperinsulinemia after RYGB. Dietary management by providing small meals with relatively low content of carbohydrates was successful in controlling symptoms. Therefore, it is important to ask adolescents about symptoms that may suggest postprandial hypoglycemia during follow-up care after weight loss surgery. (See "Bariatric operations: Late complications with subacute presentations", section on 'Postprandial hyperinsulinemic hypoglycemia'.)

●Cholelithiasis – Cholelithiasis is a common complication of any type of weight loss surgery. In the Teen-LABS study, cholecystectomy was required within three years in 8.6 percent of patients (9.9 percent for RYGB and 5.1 percent for SG) [101]. An additional 5 percent of participants required other abdominal operations, including lysis of adhesions, gastrostomy, or ventral or internal hernia repair. In a study that compared adult with adolescent outcomes of RYGB, abdominal reoperations were more commonly seen in adolescents (20 percent of adolescents versus 16 percent of adults) and cholecystectomy was the most common single intraabdominal reoperation, performed in 14 percent of adolescents and 11 percent of adults after RYGB. However, over 10 times more adults than adolescents had previously undergone cholecystectomy prior to RYGB, suggesting a difference between the proportion of adolescents and adults at risk for postoperative cholecystectomy in this study [136]. (See "Bariatric operations: Late complications with subacute presentations", section on 'Cholelithiasis'.)

●Gastroesophageal reflux – Symptoms of gastroesophageal reflux, nausea, bloating, and diarrhea significantly increased from six months to five years of follow-up in the Teen-LABS participants, as assessed by a validated gastrointestinal symptom rating scale administered at all postoperative study visits [159]. During five years of follow-up, the incidence of gastroesophageal symptoms gradually increased in both groups, rising from 11 to 24 percent in patients who had undergone SG compared with an increase from 2 to 8 percent among those who had undergone RYGB. At five years postoperatively, the SG group had a more than fourfold greater odds of having these symptoms compared with the RGYB recipients (adjusted odds ratio [OR] 4.85, 95% CI 2.63-8.91). Interestingly, usage of antireflux medications was lower among SG recipients (10 percent) than RYGB participants (14 percent) at five years. Although the prevalence of esophageal inflammation and injury among adolescent recipients of bariatric surgery is not known, based on concerns for possible heightened risk of Barrett esophagus after SG in adults, we recommend assessment for gastroesophageal reflux disease and treatment in all patients reporting significant reflux and heartburn symptoms. (See "Outcomes of bariatric surgery", section on 'Gastroesophageal reflux disease' and "Bariatric operations: Late complications with subacute presentations", section on 'Acid reflux or Barrett esophagus'.)

●Alcohol use disorder – At eight years following weight loss surgery, nearly one-half of those who underwent surgery as adolescents screened positively for alcohol use disorder, symptoms of alcohol-related harm, or alcohol-related problems. These findings highlight risk for harmful alcohol use after weight loss surgery in adolescents and provides a rationale for alcohol use disorder evaluation and treatment during follow-up for adolescents undergoing this procedure [160]. (See "Outcomes of bariatric surgery", section on 'Alcohol and other substance abuses'.)

●Revisional surgery – In adults who have undergone SG procedures, conversion to RYGB is not uncommon. Indeed, in 2020 to 2021, 86 percent of RYGB procedures were primary cases (no prior surgery) and 14 percent were "secondary" RYGB procedures (performed to convert an SG to RYGB) [161]. The most common reasons for such a conversion include severe gastroesophageal reflux (55 percent of cases) and weight regain (24 percent). (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Primarily revisional procedures'.)

Further details on late complications are provided separately. (See "Bariatric operations: Late complications with subacute presentations".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bariatric surgery" and "Society guideline links: Obesity in children".)

SUMMARY AND RECOMMENDATIONS

●Definition of severe obesity – In adolescents, class II obesity is defined as a body mass index (BMI) that is either ≥120 percent of the 95^th percentile or ≥35 kg/m² (whichever is lower) (figure 1A-B). This threshold corresponds to approximately the 99^th percentile (Z-score 2.33). Class III obesity is defined as BMI ≥40 kg/m² or ≥140 percent of the 95^th percentile of BMI for age (whichever is lower). (See 'Consequences of severe obesity' above.)

●Types of surgery – The most widely performed procedures in adolescents and adults are the sleeve gastrectomy (SG) (figure 2) and Roux-en-Y gastric bypass (RYGB) (figure 3). Other procedures that cause significant malabsorption are generally not recommended for adolescents, due to lack of safety data in this age group and concerns about long-term nutritional complications. Adjustable gastric banding (AGB) is rarely used due to suboptimal weight loss for many patients and increasing use of SG. (See 'Types of surgery' above.)

●Preoperative evaluation and screening

•Setting – Weight loss surgery for adolescents should be performed in the context of a multidisciplinary program with extensive expertise in bariatric surgery and specific expertise in adolescent medicine. (See 'Screening' above.)

•Patient selection – For adolescents less than 18 years of age, the following BMI thresholds are used for consideration of weight loss surgery (figure 1A-B):

-Class II obesity (BMI of ≥35 kg/m² or ≥120 percent of the 95^th percentile of BMI for age) with clinically significant medical comorbidities (ie, those that carry a high risk of morbidity over the short term)

-Class III obesity (BMI of ≥40 kg/m² or ≥140 percent of the 95^th percentile of BMI for age), with or without obesity-related comorbidities or impaired quality of life (based on self-report)

After 18 years of age, BMI thresholds are the same as those used for adults. Note that a BMI ≥40 kg/m² represents very severe obesity in younger patients, particularly those younger than 16 years, in whom this threshold is substantially higher than the 120 percent of the 95^th BMI percentile curve for age. (See 'Patient selection' above.)

Other criteria for patient selection include lack of medically correctable causes of obesity, adequate emotional maturity and stability to ensure competent decision-making, and good adherence to medical follow-up (table 1). In addition, most authorities agree that the patient should have failed organized and attempts to lose weight through lifestyle intervention. (See 'Patient selection' above.)

●Management

•Perioperative management – Perioperative and postoperative management in adolescents is similar to that for adults undergoing weight loss surgery. Diet recommendations vary depending on the type of procedure and vary slightly among centers. (See 'Perioperative safety' above and 'Diet' above.)

•Nutritional supplements – For all patients who have undergone RYGB and SG, we suggest treatment with a daily multivitamin, with additional supplements of calcium, vitamin B12, and vitamin D (table 2) (Grade 2B). We perform laboratory monitoring for micronutrient deficiencies at least once annually thereafter. (See 'Nutritional supplements' above and 'Nutritional monitoring' above.)

•Pregnancy prevention – We recommend avoidance of pregnancy for 12 to 18 months after surgical weight loss procedures (Grade 2B). Because adolescent females appear to be at high risk for pregnancy after bariatric surgery as compared with others in their age group, all females should have counseling about pregnancy avoidance and assurance of adequate contraception as part of the preparation and follow-up after weight loss surgery. (See 'Pregnancy prevention' above.)

●Outcomes

•Weight loss – Weight loss surgery in adolescents results in loss of between 52 to 70 percent of excess body weight. Weight loss outcomes at three years postoperatively are comparable between SG and RYGB in adolescents (figure 5). Emerging data show potential advantages of earlier surgery and good safety outcomes compared with adults. (See 'Weight loss' above.)

•Effects on comorbidities – Weight loss surgery results in resolution or substantial improvement in comorbidities (figure 6). This includes improvements in insulin resistance, diabetes, obstructive sleep apnea, triglyceride levels, hypertension, kidney function, depression, and quality of life. (See 'Outcomes' above.)

•Complications – Perioperative complications in adolescents undergoing weight loss surgery are generally similar to those in adults but occur somewhat less frequently. Long-term complications are primarily nutritional and include deficiencies of iron, vitamin B12, vitamin D, and thiamine. Lifelong vitamin and mineral supplementation is imperative. However, adolescents often have poor adherence to supplementation regimens. Other complications include risks for hypoglycemia, cholelithiasis, alcohol use disorder, and decreased bone strength. (See 'Outcomes' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Stavra A Xanthakos, MD, MS, who contributed to earlier versions of this topic review.