Body composition differences in normal weight, obese-overweight and anorexic adolescents: role of adipocytokines.

Adipocytokines are signaling molecules released by adipose tissue with numerous functions, including regulation of metabolism, inflammatory process, and body mass. They are particularly interesting in youth, considering the rising prevalence of overweight/obesity and the linkage of this condition to inflammation. This chapter examines the relationship between body composition and select adipocytokines: leptin, adiponectin, IL-6, TNF-α, and resistin, in overweight, normal weight and anorexic youth. Leptin, which stimulates energy expenditure and promotes satiety, is highest in overweight youth, followed by normal weight and lastly anorexic youth. Adiponectin has similar functions to leptin but is negatively correlated with measures of body composition. Anorexic youth have the highest adiponectin per kg fat mass, followed by normal weight and overweight. Conversely, IL-6 is positively associated with body composition; however, research in anorexic youth is inconclusive. It has some pro-inflammatory effects and promotes glucose and fat use, therefore beneficial for maintenance of normal weight status. TNF-α is also a pro-inflammatory adipocytokine thought to be somewhat protective against cancer. TNF-α is highest in overweight, followed by normal weight and anorexic youth, similar to leptin. Finally, resistin is also involved in the pro-inflammatory response and the development of insulin resistance. However, far less research exists on this adipocytokine and its relation to body composition in overweight or anorexic youth is equivocal. In conclusion, several consistent relationships exist regarding adipocytokines and body composition; however, there is a need for additional research on these relationships in youth especially at extremes of adiposity such as overweight and anorexics.