Body mass index (BMI, kg/m²) is a relatively simple means to define the term overweight in adults who have attained full growth. Adults with a BMI > 25 kg/m² are considered overweight, while those with BMI ≥ 30 kg/m² are considered obese. In children and adolescents, we expect physiologic increases in adiposity, height, and weight during growth; thus we cannot simply use a single BMI value to make accurate predictions about adiposity. Instead, for the vast majority of children and adolescents, growth charts are used to assign cutoffs for obesity that are actually age, race, and sex specific [8]. In this context, some authors have defined pediatric obesity as BMI greater than the 95th percentile for age and sex. Overweight, or at risk for overweight, has been defined as a BMI > 85th percentile [9–11]. It is important to first recognize that these percentile definitions of obesity and overweight become unreliable at the extreme categories of obesity. In essence, for the very severe categories of obesity, which might prompt consideration for bariatric surgery in adolescence, there are currently no strong, reliable population-based data by which one can calculate percentile boundaries. This is due to children and adolescents with BMI values in the >40 kg/m² range being very poorly represented in the National Health and Nutrition Examination Survey (NHANES)—the dataset that provides the weight and height information used to create the commonly used pediatric growth charts. Alternatively, most have used BMI ≥ 40 kg/m² as a conservative threshold for defining morbid obesity in youth, which is congruent with the World Health Organization definition for adults.

Adopting a BMI threshold as a general guideline for considering adolescent bariatric surgery is done with the understanding that an obese adolescent with an advanced, severe, and incontrovertibly weight-related comorbidity also should be considered for weight loss surgery without strictest regard to level of BMI.

When considering bariatric surgery among adolescents, it may be useful to identify those groups of patients who are at highest risk of persistent obesity and its sequelae. The risk of a child carrying obesity into adulthood is influenced by genetic, biological, psychological, cultural, and environmental factors [12]. There are critical phases in the development of adolescent obesity within the period between preconception and adolescence [13, 14]. In neonates, lower birth weight has been linked to higher BMI in childhood and adulthood [15–19]. Childhood obesity risks are also higher for offspring of mothers with diabetes mellitus [20, 21]. Through a recent critical review of the literature, it seems that the most critical early markers for obesity during the neonatal period are related most to maternal BMI, smoking, and weight gain during pregnancy [22]. Extended duration of breast-feeding in the postnatal period reduces the risk of adolescent overweight [23–27]. In fact, early bottle-feeding accelerates the age of obesity rebound, which predicts obesity in later life [23]. It should also be noted that those infants who grow more rapidly during the first 3 months to 2 years of life are more likely to be obese as adults [28].

Due in part to the rapid hormonal changes, puberty is also considered to be a critical period for the development of both insulin resistance [29] and obesity [30]. Interestingly, earlier menarche is seen in obese children, suggesting that the obese experience an earlier onset of physiologic maturation compared with children of normal weight [31].

Obesity in family members is an additional and important risk factor for adolescent obesity. As an example, recent evidence demonstrates that the risk for persistence of childhood obesity into adulthood is elevated threefold and tenfold if one or both parents are obese, respectively [32–35]. The risk of obesity persisting into adulthood is far higher among obese adolescents than among overweight younger children [36]. Finally, there is a preexisting racial-ethnic disparity in the risk of obesity, with lower socioeconomic groups being especially vulnerable because of poor diet and limited opportunity for physical activity [37, 38].

In summary, important risk factors for childhood and adolescent obesity include (1) low birth weight; (2) bottle-feeding; (3) maternal factors including weight, smoking habits, and diabetes; (4) rapid growth at a young age; and (5) parental obesity. Knowledge of these important risk factors for adolescent obesity and its persistence into adulthood gives some insight into the phenotypes of those individuals who may be least likely to succeed with nonsurgical management of obesity and, by inference, those who may benefit most from early application of surgical therapy.

In association with the remarkable increase in the prevalence of pediatric obesity is a parallel increase in the severity of obesity and in obesity-related chronic diseases. Important complications of obesity commonly encountered in adolescents include increased risk of cardiovascular disease (especially hypertension and left ventricular hypertrophy), nonalcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus and insulin resistance, sleep apnea, pseudotumor cerebri, and psychosocial impairment [39–42]. These diseases have an onset at a younger age and carry an increased risk for adult morbidity and mortality [43–45]. This serves to heighten awareness about the significance of medical consequences of obesity among adolescents.

There is a relative paucity of data focusing on the cardiac health of severely obese adolescents, likely due to the general belief that associated sequelae (i.e., atherosclerosis, peripheral vascular disease, etc.) become more clinically relevant later in life. However, a mounting body of evidence has demonstrated that the pathogenesis of various cardiovascular disease states can find their development and subsequent progression in early childhood and adolescence. Recent evidence demonstrates the presence of these cardiovascular risk factors, namely, hypertension, hypertriglyceridemia, elevated fasting serum glucose, and cholesterol abnormalities, as well as cardiac structural and functional abnormalities in the obese adolescent population [41, 42, 46, 47]. Almost 60 % of obese children in the Bogalusa Heart Study had one risk factor for cardiovascular disease, with 20 % having two or more risk factors [48]. Of note, following gastric bypass and significant weight loss in obese adolescents, recent data demonstrates significant improvement in left ventricular hypertrophy and overall cardiac function [41]. Gastric bypass in adolescents has also been shown to significantly improve the major cardiovascular risk, hypertension, and hyperlipidemia in those patients at 1-year follow-up [46, 49]. Large, prospective trials are currently ongoing to better investigate the cardiac health of this patient population.

Given the current increases in childhood diabetes and obesity prevalence, epidemiologists at the Centers for Disease Control and Prevention (CDC) have made a sobering prediction: type 2 diabetes is expected to develop in 33–50 % of all Americans born in the year 2000 [50]. There have also been recent reports linking the development of abnormalities related to normal glucose regulation, including hyperinsulinemia (60–80 %), impaired glucose tolerance (12–15 %), and type 2 diabetes mellitus (1–6 %) to childhood obesity [40]. The prevailing thought is that the generalized state of low-grade chronic inflammation could be a significant factor leading to insulin resistance and subsequent dysregulation (i.e., metabolic syndrome). Of note, there is not only a relationship between severely obese adolescent patients and insulin resistance (elevated hemoglobin A1c and C-reactive protein (CRP) levels), but there is significant improvement seen in most markers of metabolic dysfunction within the first year following gastric bypass and significant weight loss [46, 49].

The application of surgical weight loss procedures in the severely obese adolescent population has been an ongoing and evolutionary process over the past decade and continues to gain attention within the medical community as an effective treatment strategy. The increased interest in the use of surgical weight loss surgery in the adolescent population comes on the heels of a significant body of literature demonstrating the safety and efficacy of bariatric intervention for the treatment of severely obese adults [62, 63], as well as the disappointing results associated with attempts to lower pediatric and adolescent BMI through diet, exercise, and behavior modification [64, 65]. The increasing use of this treatment modality is further supported by an increasing body of literature reporting encouraging longitudinal outcomes for adolescents undergoing surgical weight reduction. As a result of these factors, the reported volume of adolescent bariatric procedures in the United States has risen three to fivefold between the late 1990s to 2005 [66, 67] with more recent reports demonstrating a surprisingly high number of adolescent cases being performed supporting the consensus that the rising trend continues into the current decade [68, 69]. Although an accurate accounting of the number of adolescent bariatric procedures being performed in the United States annually is uncertain at the present time, several trends have emerged with regard to the general environment in which adolescent bariatric procedures have been undertaken during the previous decade that lend support for the need to establish specific guidelines and standardization of adolescent bariatric care [67]. Schilling et al. reported that 87 % of hospitals performing adolescent bariatric surgical operations from 1997 to 2003 performed four or fewer on an annual basis and that the majority (85 %) were carried out within an adult facility. A similar pattern of adolescent bariatric care within adult facilities is seen in a more recent review of 890 adolescent bariatric procedures performed between 2004 and 2010 at 360 adult facilities in the United States [69]. Although no specific inferences can be drawn regarding the associated level of adolescent-specific resources from these reports, including whether or not an adolescent-specific multidisciplinary team was involved in the patient management process, the recent rise in the number of centers focusing strictly on the surgical weight reduction for severely obese adolescents underscores the need for standardized patient selection criteria as well as recommendations for the development of bariatric surgical centers that take into account the specific needs of this emerging population.

Early guidelines addressing the specific use of bariatric surgery in the adolescent population, first presented in 2004 [70], have been updated several times and should be referred to for in-depth consideration [71–73]. Since no national consensus conference pertaining to the surgical treatment of severe adolescent obesity has been convened as yet, the previous and more current recommendations for adolescent bariatric care have been based on modification of the 1991 National Institutes of Health (NIH) consensus guidelines for adult bariatric surgery, which offer little to no substantive recommendations for the surgical care of the severely obese pediatric population. In contrast to the initial report by Inge et al. [70], current recommendations have undergone a shift toward a less conservative approach that has become more consistent with the widely accepted adult eligibility criteria and appear to reflect a general consensus among centers providing adolescent bariatric surgery at this time. Although several of the initial recommendations have been modified based on nearly a decade’s worth of experience since the original publication, the most significant departure relates to the assessment of preoperative BMI with regard to surgical eligibility (i.e., originally recommended to be BMI ≥ 40 kg/m² with serious comorbid conditions and BMI ≥ 50 kg/m² with less severe comorbid conditions). In addition to an expanding body of literature demonstrating safe and efficacious outcomes that support the shift toward a lower than previously recommended BMI range, recent observations demonstrating a potentially fixed “ceiling” effect (i.e., maximal expected reduction in BMI) among adolescent bariatric patients suggest that the earlier timing of bariatric intervention (i.e., at a lower BMI) may result in a high propensity to achieve an optimal postoperative result (i.e., BMI ≤ 35 kg/m²) [49]. As the number of healthcare institutions providing bariatric surgical care for the severely obese adolescent population has increased, a parallel consensus has developed regarding a number of key elements that serve as the foundation for an adolescent-specific multidisciplinary team approach, which are briefly reviewed herein.

In a recent effort to establish a more uniform approach to adolescent bariatric surgical care in the United States, national accreditation guidelines for adolescent bariatric care are presently under development and are expected to be fully incorporated within the newly developed Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) which is expected to replace the previous independent bariatric standards and accreditation programs separately administered by the American College of Surgeons (ACS) and the American Society for Metabolic and Bariatric Surgery (ASMBS) in the near future. The fundamental components representing previously published best practice recommendations will be included and are presented below [72–74]. The effort to provide widely accepted standards for the treatment of the severely obese adolescent population will most likely occur in one of several programmatic models (i.e., an adult facility vs. a pediatric facility under the direction of an adult bariatric surgeon, a pediatric surgeon specializing in bariatric care, or a combination of the two). The following key items are presented for consideration herein as a general overview and do not take into consideration institutional-specific logistics and available clinical resources at the local level:

In addition to the recommended adolescent-specific resources outlined above and in keeping with the multidisciplinary care model, the development of an adolescent bariatric surgery program should include the establishment of a formal multidisciplinary adolescent bariatric committee designed to review individual cases that are being considered for surgical intervention. The committee, consisting of core members (i.e., surgical and medical director, dietician, behavioral specialist, and program coordinator), should meet on a regular basis to review patient-specific information. In addition, ad hoc members of the review committee may include subspecialists such as experts in adolescent pulmonary medicine, hematology, cardiology, endocrinology, and medical ethics (including formal involvement of the institutional ethics committee when considered necessary).

As mentioned earlier, the development of criteria for adolescent bariatric patient selection has been an ongoing and evolutionary process which, since its earliest recommendation, has been based on a modification of the adult surgical patient selection guidelines defined by the 1991 National Institutes of Health (NIH) consensus panel on bariatric surgery [70–72, 74]. Because all adolescent boys and most adolescent girls <18 years of age with a BMI of 35 kg/m² correspond to BMI percentile of 99th percentile for age, the application of adult selection criterion based on BMI appears to be appropriate [40], with a more conservative approach regarding the incorporation of associated comorbid disease thresholds [72, 73]. Currently, recommendations for selection criteria for adolescent bariatric surgery based on preoperative BMI and examples of associated obesity-related comorbid diseases are seen below:

Since adolescence represents an extensive period of substantial growth and maturation, both physically and emotionally, special attention to developmental issues in adolescents is critical when considering bariatric procedures that will have marked impact on future growth and development. For adolescents who have attained the vast majority (>95 %) of linear growth, there is clearly little reason to believe that growth would be impaired by a bariatric procedure. Based on peak height velocity measurements in normal-weight girls (8–9 cm/year) and boys (9–10 cm/year), girls should achieve >95 % linear growth by 13 years of age and boys by 15 years of age [75]. The onset of menarche is also a marker for physiologic maturity in girls, and growth is generally completed within 2 years after menarche. Bone age can also be assessed by plain radiography of the hand and wrist if there is uncertainty about status of physiologic maturation. Nomograms are used by radiologists to accurately predict the percentile of adult stature that a child has attained.

While overall physiological assessment is an important foundation during the patient selection process leading up a weight reduction surgery, additional factors are equally important and include several that distinguish themselves from the routine preoperative evaluation process in the corresponding adult bariatric population. In addition to individual BMI and comorbid disease status, as the basis of eligibility criteria, assessment of the adolescent patient’s psychosocial maturity level, including the ability to demonstrate a general understanding of the benefits and risks of bariatric surgery, has been shown to be an important factor in determining eligibility. Although the factors related to maturity and general comprehension regarding bariatric surgery among adolescents are only now beginning to emerge, preoperative evaluation should attempt to determine an adolescents patient’s ability to demonstrate the ability to comply with nutritional guidelines prior to surgical intervention. Despite the paucity of data regarding the advisability of mandatory preoperative weight loss and its ability to offer predictive value regarding postoperative dietary compliance, it is currently recommended that the adolescent be able to successfully demonstrate stabilization of preoperative weight (i.e., avoid significant weight gain) prior to surgical intervention. In addition, it is considered extremely important to assess the quality of the patient’s “support mechanisms” (i.e., home environment, parental/caregiver status, etc.) in an effort to determine the likelihood of postoperative nutritional and behavioral compliance as well as the ability to comply with required postoperative follow-up. Finally, adolescent bariatric surgical intervention should take into consideration the overall risk-benefit ratio related to the progression of untreated or poorly treated comorbid diseases (i.e., type 2 diabetes, hyperlipidemia, hypertension, etc.) if left untreated. As mentioned earlier, this may include the decision to seek input from an institutional medical ethics committee in certain cases when needed.

Currently, the most commonly performed bariatric procedures in the adolescent population are the Roux-en-Y gastric bypass (RYGB), the adjustable gastric band (AGB), and the more recently introduced vertical sleeve gastrectomy (VSG). The successful use of the duodenal switch has been reported in this population [76], but is generally considered more complex and with its associated significant malabsorption and nutritional complications is not commonly performed. In general, published literature suggests that overall weight loss, resolution of comorbidities, and safety are comparable to or better in adolescents when compared to adults [49, 77, 78].