Physiological regulation of body weight and the issue of obesity

The relationship described here between resting energy expenditure and the body weight set-point provides a framework for assessing an animal's regulatory status. Procedures based on this relationship have been used to evaluate the status of rats whose obesity was either of dietary or hypothalamic origin. In dietary obese rats, the body weight set-point appears to have elevated. Their normal rate of energy expenditure at an elevated weight, as well as their active adjustments of expenditure in defense of their obesity, supports this conclusion. Hypothalamic obese rats, in contrast, neither expend energy at a rate normal for their body mass nor display the adjustments in expenditure appropriate to defending their obesity. From these observations, a distinction is drawn between regulated and unregulated forms of obesity. It is suggested that weight disorders in humans, particularly obesity, may be amenable to similar sorts of analysis and categorization, eventually leading to the development of therapies appropriate to the specific type or form indicated.