Regulation of Body Weight in Humans

Overweight and obesity among adults has dramatically increased in the last 50 years in the United States, although more recently the trend being that of a slight plateau. However, the rise of obesity in children has continued to increase, which is a major health concern for future generations. Body weight regulation is typically thought of as a balance between energy intake and energy expenditure, but other physiological and environmental factors likely contribute to the epidemic of obesity. These factors may influence the mechanisms regulating energy intake and energy expenditure but also indirectly reprogram the genetic and epigenetic background of human beings predisposing future generations to weight gain and adiposity. The environments that we reside in and how we adapt can also influence the obesity epidemic. In addition, more emphasis is being placed on the macronutrient content of diets. Not only are the typical low-carbohydrate and low-fat diets playing a role, but low-protein diets may have a new place in the regulation of body weight. Although the effects of each macronutrient may be slightly different, it seems be the case that weight loss still follows a simple negative energy balance. Weight cycling resulting from repetitive intentional fluctuations in weight loss and weight regain is becoming more prevalent as well and could have negative implications on health. This chapter will begin with a brief overview of the current state of obesity in the United States, discuss how body weight is regulated in humans and will follow with discussion of some of the key environmental and physiological factors proposed to contribute to epidemic of obesity. For complete coverage of this and all related areas of Endocrinology, please visit our FREE on-line web textbook, www.endotext.org.