About 25% of children are overweight or obese, according to newly established national criteria. These teens are at significant risk for becoming obese adults, and adolescent obesity predisposes to a range of medical and psychosocial problems. Despite the enormous medical and economic implications of obesity, effective prevention and treatment strategies are lacking.

First, it is important to distinguish the term obesity, used to describe excess body fat, from other forms of overweight, such as increased muscle mass associated with weight lifting. Recent data support the use of BMI ( body mass index) as an appropriate measure of adiposity, especially in adolescence, since it accounts for linear growth. It is recommended that 95^th percentile be used to define obesity, and the 85^th to 95^th percentile can be used to identify those at risk for obesity, and these individuals are described as overweight.

Epidemiology

The National Health and Nutrition Examination Survey (NHANES) has monitored changes in body weight among children and adolescents in the US since the 1960ís. According to data from the most recent survey, (NHANES III) 14% of children and 11% are obese. These figures represent a twofold increase in prevalence rates since NHANES I.

Obesity in all stages of life is thought to be the result of both genetic and environmental influences. Studies on identical and fraternal twins raised together versus those raised apart suggest a strong genetic influence on BMI.

Genetic influences:

• mutations in genes that encode leptin
• leptin receptor
• proopiomelanocortin

• food availability
• portion size
• sedentary lifestyle
• television viewing time

So the teen is overweight? Whatís the big deal?

There is an important association between obesity and a variety of immediate and long-term health concerns.

• Orthopedic problems such as slipped capital-femoral epiphysis and Blountís disease are found predominantly in obese adolescents
• Pseudotumor cerebri
• Sleep apnea
• Gallbladder disease
• NIDDM
• Hypertension

In addition to the medical complications, adolescent obesity has serious psychological consequences. Obese adolescents have lower self-esteem, and follow-up studies of patients who were obese as adolescents show differences in long-term outcomes in adulthood, such as:

• lower education levels
• lower incidence of marriage
• lower household incomes
• higher rates of poverty

Conversely, psychosocial problems may predispose to obesity. Those who experienced abuse had a 1.4 to 1.6 fold increase in physical inactivity and severe obesity.

Treatment

Treatment of adolescent obesity is controversial and difficult. Many topics need to be addressed in the initial evaluation, such as:

• diet history
• culturally determined food preferences
• level of physical activity
• presence of behavior disorders
• family dysfunction

A successful obesity regimen has been described as one that prevents increased weight gain, causes a 5% to 10% reduction in initial body weight, and establishes long-term maintenance once weight loss goals are achieved.

Interventions:

• Increasing physical activity
• Decreased television watching time
• Encourage participation in physical education classes
• Introduction of daily activities such as using stairs, etc.
• Dietary interventions
• Reduction of dietary fat is essential, through diets such as the "stoplight" diet, which limits high-fat and high-calorie foods by grouping into usable categories that allow the patient to make food choices regarding the meal plan.
• Introduction of a ketogenic diet, which has been shown to obtain rapid weight loss in highly motivated patients. The diet consists of 80-100 g of protein, 25 g of fat, 25 g of carbohydrate, totaling 700 calories per day. This is a temporary diet for at-risk patients, and controversy remains regarding the long-term efficacy of this plan.
• Dietary glycemic index diet. The glycemic index describes he degree to which blood glucose rises after a meal. Refined, starchy foods, like bread, cereal and potatoes and concentrated sugars have a high glycemic index, whereas most vegetables, legumes and fruits have a low GI. Studies have shown that after a high GI index meal, blood glucose and insulin levels generally rose higher than after the low-GI meal. A few hours after the high GI meal, blood glucose and fatty acids decreased to relatively low levels an epinephrine rose markedly. These metabolic changes are associated with increased hunger, and subjects were found to eat 80% more calories after the high GI meal versus the low GI meal. Thus, a low GI diet may help decrease hunger and promote weight loss.
• Drugs
• The use of drugs in adolescent patients is not recommended at this time, however, several new drugs are under investigation.
• Sibutramine (Meridia) is a serotonin and noradrenaline reuptake inhibitor that has been shown to increase energy expenditure and satiety in clinical trials
• Orlistat (Xenical) reduces the absorption of fat from the GI tract by blocking pancreatic lipases. Use of this drug has been shown to reduce weight, improve LDL cholesterol and circulating insulin levels.
• A novel approach to drug therapy may be leptin and leptin receptors. Leptin is a circulating hormone produced primarily in adipose tissue that induces profound changes in hunger and energy homeostasis, presumably through interaction with receptors in the hypothalamus. Clinical trials with leptin administration are currently under way.
• Surgery
• Although effective, ileojejunal bypass surgery has major medical risks, including fatal intraoperative complications, wound dehiscence, pain, diarrhea, electrolyte disturbances, and nephrolithiasis. New laparascopic techniques may prove to have fewer complications, however, little research has been done to assess the long-term effects of gastric bypass in adolescent patients. Surgery should only be considered in patients who are extremely obese patients who are suffering major complications and in whom conventional treatment has failed.
• Multidisciplinary approaches are generally the most effective. Team approaches that involve the collaboration of pediatric subspecialties are appropriate for children and adolescents that are at risk. The physician conducts a medical evaluation to rule out underlying endocrine, metabolic, or genetic conditions. The nutritionist obtains a detailed diet history, identifies problem areas such as skipped meals and excessive fruit juice or soda consumption, and works with the family to set realistic goals for dietary change. The behavioral medicine specialist assesses the adolescentís level of motivation, relevant family dynamics, and any obstacles to effective lifestyle modification.