Childhood overweight: an expanding problem.

Childhood overweight is a significant and growing health problem in the US and other parts of the world. Secular trend data in the US suggest that children have become substantially heavier over the last several decades and that their risk for a number of health problems is increasing as a result. Defining obesity in children has been difficult as assessing body fat is expensive and impractical. Body mass index (BMI), derived from weight and height, is used as a surrogate indicator in adults. In children, the consensus is to use BMI percentiles statistically derived from a reference population. There is evidence that the prenatal, early childhood, and adolescent periods are critical in the development of obesity but the mechanisms involved are yet to be elucidated. The recent rapid increase in childhood overweight and obesity is attributed to the modern obesogenic environment. Changes in dietary constituents including higher derivation of energy from nutritionally poor and energy dense foods, increased sweetened drink consumption, larger portion sizes, and more frequent intake of food outside the home have been associated with poorer diets and higher weights. Further, physical activity has reduced with decreases in school physical education classes and organized sports, fewer opportunities to expend energy for daily living activity due to more mechanization, lower frequency of walking and biking, and greater use of sedentary activities for leisure. Television watching remains the most common activity for children. There are significant health outcomes associated with childhood obesity, including the presence of cardiovascular risk factors, and greater prevalence of various medical problems including insulin resistance, type 2 diabetes mellitus, the metabolic syndrome, orthopedic problems, and pseudotumor cerebri. Of further concern is the increased risk for obesity in adulthood with its attendant co-morbidities. Interventions are imperative but not widely studied. The most effective interventions include comprehensive behavioral management, dietary modification, and exercise. Family-based interventions have been most successful at maintaining long-term weight loss. School-based interventions have the potential to significantly impact childhood overweight as large numbers of children can be reached. However, such programs require long-term follow-up and are expensive. Very low calorie diets, pharmacotherapy, and surgery remain experimental options for children. More recently, metformin has shown promise in promoting weight loss and improving insulin sensitivity among adolescents. Combining multiple approaches for treatment, addressing obesity-promoting sociocultural practices and policies, and focusing on prevention strategies will be necessary to address this epidemic.