
Background: A positive relation between high fat diet and obesity is well documented. The amount of total energy required by an organism derived from each component of diet affects the weight. But if the total calories in diet of an experimental animal is constant (isocaloric) irrespective of its constituents, it is least likely to increase the weight of these animals. The present study was done to observe the effects of isocaloric diet with different percentage of the constituent components on the weight of Albino rats. Methods: The present study was done for a period of 24 weeks. Thirty male albino rats taken for this study were randomly divided into three groups A, B and C with 10 rats in each group. Group A rats served as control and were fed on low fat diet consisting of chow containing 2.5 percent of fat. Group B rats were fed on isocaloric but high fat diet (30% of total calories were derived from animal fat). Group C rats were fed on high caloric high fat diet. The mean weight of these animals was taken at the beginning and at the end of this study. Results: The mean weight of animals fed on isoclaoric diet irrespective of its components was same. The animals fed on high fat high calorie diet gained more weight. Conclusions: The results of this study show that isocaloric diet irrespective of its components (high fat verses low fat) does not affect the weight of Albino rats. It is the total number of calories irrespective of dietary components that results in weight gain of Albino rats.