BODY-WEIGHT SET-POINTS - DETERMINATION AND ADJUSTMENT

It is proposed that body weight, like body water and body temperature, is physiologically regulated. In the case of body weight, coordinated adjustments in both the intake and expenditure of energy serve to sta bilize the weights of individuals at a specified level and to resist t heir displacement from this level. Obese individuals also display thes e behavioral and metabolic adjustments to weight perturbations and thu s appear to actively resist efforts to reduce their weight from the el evated levels they ordinarily display. Experimental studies of genetic ally transmitted and diet-induced forms of obesity in animals similarl y suggest a view of obesity as a condition of body energy regulation a t an elevated set-point. An individual's set-point for regulated body weight is apparently adjustable, shifting over a lifespan in conjuncti on with naturally occurring but still unspecified physiologic changes. Experimentally, the set-point for body weight can be adjusted by mani pulation of specific hypothalamic sites. Lesions of the lateral hypoth alamus, for example, cause a chronic reduction in the level at which l aboratory animals regulate body weight. It thus appears that hypothala mic mechanisms play a primary role in setting the level at which indiv iduals regulate body weight, and it is likely that the genetic, dietar y and other lifespan influences on body weight are expressed through t hese mechanisms.