Obesity in Children and Adolescents: Working Group Report of the Second World Congress of Pediatric Gastroenterology, Hepatology, and Nutrition

TABLESUMMARY OF THE PROBLEM Obesity is defined as an excess of body fat. It involves both genetic and environmental influences and is associated with >40 different medical and psychological problems. Thus, obesity places an enormous social and economic burden on most societies, making it the most important nutritional disease in developed countries. The continuous variations in height and relative muscle mass show that obesity cannot be evaluated by weight measures alone, particularly in the case of children and adolescents. Body mass index (BMI; weight in kilograms divided by height in meters squared) is a useful measure of adiposity because it accounts for variations in height. Availability and palatability of food and low levels of physical activity are frequently associated with increasing obesity in most populations. These patterns appear to be transferable from one population to another and affect immigrants as they assimilate into a new culture. However, determining the key elements of the diet or lifestyle that predispose to obesity remains challenging and is an essential focus of research. Studies of twins and adoptees provide useful estimates of the role of heritable factors in determining an individual's body weight (see Bouchard's 1997 summary of relevant papers on heritability) (1). Adoption studies tend to generate the lowest heritability estimates (30%), whereas twin studies provide the highest heritability estimates (70%). The variability in these estimates of heritability depends in part on definitions of obesity: more severe obesity tends to have a greater heritability factor than less severe obesity. There is evidence that nutrition during early development may have permanent and long-term effects on the risk of future obesity. This “metabolic program” conspires with genetic factors to create a “set point” that affects an individual's body weight throughout the lifespan. Various factors have been associated with the development of obesity: intrauterine environment, diabetes, maternal smoking, duration of breast-feeding, early feeding practices and complementary food introduction, and weight gain in early childhood and during puberty. Thus, interventions to prevent obesity should target these periods. Most of the complications typical of adults and older people are now appearing in children and adolescents. Psychosocial dysfunctions, isolation, depression, and low self-esteem are often early consequences of obesity, whereas cardiovascular risk factors and diabetes are usually long-term complications of excess weight. The management of obesity in children and adolescents must include preventive and treatment programs designed to support healthy diet and physical activity; nutrition education at all levels, in homes, schools, and canteens, must be associated with physical activities aimed at prevention and cure. Currently, drugs are not considered safe and effective for all ages and should be reserved for cases that do not respond to behavioral treatments. Surgery is a last resort option in carefully selected severely obese adolescents, especially those with severe metabolic disturbances. Prevention is the best way to combat obesity. Government, industries, and local networks could contribute to preventive measures, eg, providing physical activities, preventing the consumption of unhealthy meals in schools, and continuing education programs for health-care and related professionals. ASSESSMENT OF OBESITY Clinical Anthropometry and Classification of Excess Weight Develop and Validate a Universal Clinical Classification System for Excess Weight and Treatment Standards for Obesity-Related Complications BMI is a practical and useful measure of adiposity because it accounts for variations in height. By convention, obesity is defined as a BMI of ≥30 in adults. There is a strong but imperfect correlation between BMI and body fat. For children and adolescents, adiposity varies by age and gender; thus, BMI percentiles are the appropriate standard. In the United States, “overweight” is defined as a BMI over the 95th percentile for age. The US Centers for Disease Control recently developed new reference charts. In an effort to describe a healthy population and to track trends in obesity over time, the BMI for age reference charts was prepared from national surveys; for some age groups recent weight data were not considered because of rapid increases in obesity in this population during the past decade. The International Obesity Task Force (IOTF) has developed a definition of overweight and obesity for children and adolescents based on nationally representative growth studies from six countries (Great Britain, Brazil, the Netherlands, Hong Kong, Singapore, and the United States). The cut points for obesity and overweight were based on the BMI for age centile curves that, at 18 years of age, pass through the widely used adult cut points of 25 and 30 kg/m2, respectively. These age- and sex-specific BMI cut points developed by Cole et al (2) are very useful for epidemiological research because they are applicable to an international population and can be used to compare populations worldwide. However, as the authors acknowledge, the reference data set may not be representative of non-Western populations. BMI measurements are useful for epidemiological studies and are clinically practical estimates of obesity. However, BMI can overestimate or underestimate body fat considerably because of variations in lean body mass between individuals and between ethnic groups. Direct measures of body fat may be necessary for physiological studies and require the use of specialized calipers or expensive procedures such as dual energy x-ray absorptiometry, magnetic resonance imaging, or plethysmography. There is a need to accomplish the following: Develop guidelines and classifications of obesity and overweight for children and adolescents, as well as anthropometric references and approaches that can be used in epidemiological studies worldwide. Study the validity of using the IOTF BMI standards to make international comparisons and to monitor secular trends in childhood obesity, especially in developing countries where children and adolescents have very different patterns of growth and development compared with their counterparts in industrialized countries. Collect national longitudinal data in developing countries to study the problem of childhood obesity, especially in older children (>5 years of age) and adolescents. Conduct Studies to Clarify the Prevalence and Incidence of the Complications of Overweight and Obesity in Childhood and Adolescence: Large-scale prospective population studies should incorporate careful anthropometric measurements and regular monitoring of selected obesity-associated complications using some or all of the following tests: fasting blood tests (glucose, insulin, lipids, liver function tests), blood pressure measurement, glucose tolerance test, liver ultrasound, measurements of psychosocial functioning, lung function tests, and biomechanical or podiatric assessment. This approach would reveal the prevalence of obesity-associated complications in the general population and the incidence of new cases. Note that some complications lend themselves to measurement in population surveys (eg, hypertension and biochemical abnormalities), whereas others may not be identified (eg, obstructive sleep apnea). Agencies to be involved and funding opportunities include IOTF, WHO, non-governmental organizations, and UNICEF. Coordinated multicenter studies of clinical populations of overweight and obese children and adolescents should incorporate careful anthropometric measurements and regular monitoring of selected obesity-associated complications, ie, fasting blood tests (glucose, insulin, lipids, liver function tests), blood pressure measurement, glucose tolerance test, liver ultrasound, measurements of psychosocial functioning, lung function test, biomechanical or podiatric assessment and sleep studies. Develop Effective Interventions for the Complications of Overweight and Obesity in Childhood and Adolescence. Coordinated multicenter studies of interventions in clinical populations of overweight and obese children and adolescents must be implemented. Whenever possible, the studies should be randomized controlled trials. The studies should examine the following clinical issues: for glucose intolerance and hyperinsulinemia, insulin-sensitizing agents (eg, metformin) and lifestyle intervention (different aspects, eg, types of exercise, types of dietary interventions, level of intensity, and support given); for NASH, insulin-sensitizing agents, various lifestyle interventions, and antioxidants; and for obstructive sleep apnea, tonsillectomy/adenoidectomy, continuous pressure airway, and weight loss interventions. Genetics We must advance our understanding of the physiological and genetic determinants of body weight to establish appropriate treatment for the severely obese. Moreover, understanding the mechanisms underlying the genetic components of more moderate obesity, which seems to be induced by cultural and environmental influences, is likely to allow better targeted efforts to modify these environmental influences. The pediatric research community should play a central role in this field because of its unique access to severely affected individuals and their families. Association studies use a case-control design to assess the association between variations in genotype and obesity phenotype. This technique lends itself to the testing of several polymorphisms in candidate genes within a population; however, it is prone to substantial false-positive and false-negative results, depending on sample size. Therefore, the results of association studies are useful if similar gene associations can be demonstrated in several different populations. The technique has been used to analyze many candidate genes from the afferent and efferent pathways mentioned above in genetically similar populations (siblings, twins, or By polymorphisms candidate genes been to have some association with obesity eg, and the In of populations are used to assess the of the association between variations in a and the phenotype. The of to obesity is Studies of populations have identified many that are associated with a of eg, levels, fat and such been identified as of the gene some of which appear to the of identified candidate genes such as the or of genetic patterns of and a that obesity have been identified and in the in of these have been to one or more There is strong evidence that some influences during and early childhood may have permanent effects on the “metabolic determining weight in are maternal diabetes and use during Studies in and are necessary to the physiological mechanisms underlying this metabolic designed intervention studies are to of some of these factors such as maternal weight and early childhood feeding patterns the risk of obesity in the genetic of obesity and the of metabolic to the to clinical include developing a of to allow the development of and of the pediatric research community in genetic studies of populations. This require careful to in genetic studies be by of the problem of obesity and of the of understanding the underlying genetic and physiological of Clinical and Complications of Excess Weight children and adolescents from all body The effects include social and psychological and medical whereas the long-term effects include the of risk factors for cardiovascular disease and diabetes and the development of adult obesity. Complications The most consequences of obesity in childhood and are those related to psychosocial and social children an overweight body with social functioning, and and is evidence to that self-esteem is affected in obese However, studies of adolescents show an between weight and both self-esteem and body Obesity in is related to body a for and are very body and physical it is not that the social associated with obesity in many have an on adolescents. Overweight in may be associated with social and economic in the prospective study from the United has that are overweight in are more in early to have and than with of physical are not These social obese complications that more in obese children are and with lean obese children are more likely to with at an age and to have complications of obesity include by activities and a liver on and often associated with and glucose has been as a of in Obesity is the of in children medical problems. and are complications of childhood obesity and appear to be a of pressure from and fat. studies have an association between childhood and the of this association is not Overweight children with more severe than do lean children with and they require more and more treatments. sleep may in obese children and is usually associated with and especially central obesity, in childhood is associated with risk factors for disease and is frequently with the by levels of and and levels of of the metabolic such as hyperinsulinemia, and are in children with central obesity. The incidence of diabetes children and adolescents is increasing and is to the prevalence of obesity The early and increasing prevalence of this disease could a problem as more people long-term complications at Complications The most long-term of childhood obesity is its into with all the This is more likely if is a of obesity, obesity in childhood or and severe obesity. and and blood pressure are from childhood into with obesity at a of adult Overweight in is associated with long-term and a that is of adult weight and several long-term studies have relative risk estimates of for and for from disease for overweight children and adolescents compared with their The recent obesity has been associated with increases in medical complications of obesity for which is often not Treatment of obesity and obesity-associated complications in different (eg, community have different for and of Overweight and Obesity in Childhood and can be as or Direct are those related to the use of the in the treatment of obesity and its from a or of to the or the as a of disease or are related to the social and associated with obesity. The prevalence of overweight and obesity in childhood and with the of obesity-associated complications, that be a in the use of as a of obesity, as well as a in from the burden of this data have been on the economic of obesity in childhood and the economic of obesity may to provide for interventions to prevent or overweight and obesity. Develop programs for in the and treatment of the medical and psychological complications of obesity. to this the of Overweight and Obesity in Childhood and Adolescence. The following are of the types of studies that are at the national for treatment of overweight and obesity in for treatment of obesity-associated complications to be and for treatment of obstructive sleep apnea, diabetes NASH, complications, psychological of obesity in childhood and of obesity in childhood and eg, of and of treatment and prevention interventions. Develop and for in the and Treatment of The approach to and for and treatment of obesity-associated complications varies between countries. the medical education need to be at the national level than These need to be with the medical education for the treatment of obesity not its of the of or programs that could be developed or better used are for use by with to ethnic (2) of in programs aimed at of children and at the programs with the treatment of complications such as and sleep and and for the eg, of and and and for use at the eg, medical and OF OBESITY of Obesity It is not and factors have to the secular trends in childhood obesity. Moreover, is a need to the of future obesity and of the associated medical within lifestyle factors and physical and clinical risk factors cardiovascular studies in populations that behavioral are important in obesity prevention and particularly than the are the for that on can be of the that have been for the treatment of pediatric obesity that most have a many studies of to prevent childhood obesity are by sample and of the population not physical activity to physical and and the increasing use of have to physical and less is on and on and energy is often of these can and should be by careful and that and support physical For children and adolescents, is the most to physical can provide and opportunities for play and to For and programs are safe to and can physical and affect physical the programs to physical activity is the in Brazil, which a population of individuals It was in 1997 and involves and of its the was to the and adolescents, the and and as a for programs in countries. The of healthy has been in many and an of physical activities and education on nutrition and of related to smoking, and in the The in and others are of such programs in which and dietary approaches are to healthy lifestyle in a In dietary trends have with or fat of these trends are by the food but by cultural have been such a dietary worldwide. if can be or to their for healthy support a education and could the use of fat the use of and the use of for and an and of and in of the evidence in support of such dietary is to a and to or to and food programs can to healthy by careful and in the to provide and local food may such access to less healthy such as those in is considered or in some practices dietary and in has effects on both for and of their some could from research has that many are particularly and to as is and Brazil, could to prevent obesity. has been the between physical activity and obesity in but strong evidence that and lifestyle activity are related to the of obesity, particularly in older children and adolescents. studies are to between activity patterns and in body weight. for that the for obesity prevention and to healthy the of such interventions, and their practical and effective to physical activity and in children and adolescents, particularly through programs that can be to populations. the of the of such as and the role of and of providing food in in obesity. the of in to These be effective and a must local and national It must be and based on clinical should be in representative be and be to These include support for intervention studies of the effects of factors on the long-term risk of obesity in a maternal weight and diabetes and during (2) effects of on influences and mechanisms of role of and of feeding practices or physical activity patterns in childhood or way to this is to studies that may on the physiological mechanisms underlying “metabolic during and Most research related to obesity in pediatric populations has been or on physical or behavioral interventions to the studies have preventive in a but population the from and intervention studies can the and design of future studies of obesity and and to such depending on the and of the and on are to establish and to the of unhealthy in others are to by the food the US food was the target of However, can be must establish the of diet and the of used to lifestyle countries of food and of food or in schools, ie, the of and is and may Moreover, may to such as or food from There is a need for research to establish appropriate and effective of lifestyle in different cultural economic and must be by nutritional and by not by or groups. prevent obesity, and must have the and all must be involved in funding must the of the and programs must be designed to a of age and cultural populations. medical education must of and by way of the of practices to in or in to and to these programs the of physical activity and healthy to this education to physical activity and a healthy diet by and and programs in that are to the and of the local of and to of of to be effective in one community to allow of these practices in OBESITY Obesity treatment should at the long-term of body weight and body fat within the with a of ie, psychosocial and physical and or very Most treatment focus on dietary and and physical activity and The long-term to of obesity treatment programs is not it to be better in children than in adults. Therefore, new approaches to the treatment of obesity and their to pediatric populations should be There is a need for more data and the general and the medical widely that the obesity results from an of and physical These are in dietary by the food that fat and and consumption of In the use of a diet is for weight This has been by the that with a index may contribute to the The is related to the blood glucose to a food compared with or and tend to have The of a is by and and The role of the in pediatric obesity remains However, have in obese children and adults. multicenter and studies have not been in it is early for with severe obesity may from a diet such as a of this diet include rapid weight loss to and of food which is to be related to Complications can include and to be effective medical and they in more rapid weight loss than dietary and behavioral at in the However, are data on the long-term in In are guidelines the of dietary or approaches to weight loss a Most adults on such the weight they treatment programs and programs have been effective in the with some effective in the these programs cannot as treatment because the used were treatment programs were not and several they may be useful in they are very in the treatment of and (2) they are an appropriate controlled for the development of a of treatment and to the obesity of the drugs used to obesity in adults have been by and in adults to be effective in with dietary and In weight on of The US and has drugs for obesity treatment in but are data the in an by and Weight loss is to and weight is the is effects include increases in blood pressure and and fat and by effects are related to fat with meals and in levels of weight loss is more than this was by the and for use in adolescents. or are for more than of US but are and used for weight include and adolescents and may that are some of these may have Therefore, should their the use of these and of Surgery the past induced weight loss has as an important option for adults with severe obesity. In to long-term for of obesity, approaches and substantial weight than of at of their excess body weight during the and many of the medical complications of obesity, diabetes and obstructive sleep apnea, and include and Complications of include and monitoring of selected particularly and is data on in obese adolescents that and long-term and complications are similar to those in adults is the long-term effects of weight loss in may have unique metabolic and psychological to this the of and and their and long-term multicenter studies are to can prevent and obesity in the Studies are to the long-term of such as a diet in severely obese children and the of and for the prevention of multicenter studies are to the and of treatment in the long-term of obesity. Studies should and the best for dietary and behavioral for use in multicenter studies of in (2) which overweight children are most likely to from the prevalence of dietary use and the of use in overweight and adolescents and the of and dietary and study to which severely obese children should be considered for it is appropriate to on obese adolescents or the in adolescents, the psychological and in adolescents and the long-term medical and nutritional complications in adolescents to the the related to the role of the are research it be necessary to research in this and for using a diet in children should be to long-term between pediatric research groups and the is necessary to research studies to better the and of for the treatment of childhood of multicenter of adolescents should be assessment and is this option is and long-term should be The recent rapid in obesity cannot be by in genetic The education focus of the past to fat has and the has been to a of some with dietary approaches are by and education efforts should be of to the has a risk of to with evidence for and for at to the education to the of these should be for education dietary for obesity and the of and unhealthy to these and respond to in the unhealthy practices and of The and of weight loss drugs and in adolescents and children is not multicenter of and are in adolescents, from these drugs is likely to be and the drugs are likely to have a role in the treatment of children with obesity, those with severe However, as to the determinants of body more effective drugs may careful may an important treatment Weight loss may be an appropriate option in carefully severely obese adolescents, particularly those with severe data on the long-term and are to establish guidelines in assessment and is this option is and long-term should be for obesity and its to these education and on appropriate use of and measures to obesity as by studies of these between and for this Obesity is a with and and and economic in clinical interventions, and and education be the can be The above for efforts in of these but are many important that must be by the