Influence of Body Weight and Body Fat on Appetite of “Normal” Lean and Obese Rats ‡

At least three theories have been advanced to account for the phenomenon of appetite regulation. Brobeck1 has suggested that eating is related to the homeostasis of body temperature; Mayer considers satiety and hunger to be under the influence of a glucostatic mechanism,2 Kennedy has presented evidence that inversely correlates appetite with body fat content.8 All these proposals invoke the central nervous system as the site of integration between stimulus and response;' at least two hypothalamic centers have been identified as participating in the control of food intake." The technique of forced feeding makes possible the production of obesity in the absence of genetic aberrations or any proven abnormality in the hypothalamic appetite regulating centers. Thus, an obese test animal can be provided for contrast with an animal of normal weight for the study of appetite regulation. These conditions are the opposite of those customarily employed, whereby test and control animals are of normal weight at the start of the experimental regimen. The results reported below are concerned with food intake and body weight changes in animals allowed free access to food, after having been force fed for three months and maintained either at a normal body weight or fed to double this body weight.