Studies on rats maintained on low-protein-calorie diets during the lactation period show that food intake decreases. This process results in weight loss and a delay in litter development. The purpose of the present study was to determine the alterations in food intake, maternal weight and litter growth during lactation when dams were exposed to diets with different levels of protein and carbohydrate. Female Wistar rats receiving one of 4 different diets, A (N = 14), B (N = 14), C (N = 9) and D (N = 9), were used. Diet A contained 16% protein and 66% carbohydrate; diet B, 6% protein and 77% carbohydrate; diet C, 6% protein and 66% carbohydrate; diet D, 16% protein and 56% carbohydrate. Thus, C and D diets were hypocaloric, while A and B were isocaloric. The intake of a low-protein diet in groups B and C affected the weight of dams and litters during the last two weeks of lactation, while the low-calorie diets limited the growth of D litters at 21 days compared with A litters, but had no effect on the weight of D dams. Group B showed an increase in intake during the first five days of lactation, resulting in a behavioral calorie compensation due to the increase in carbohydrate content, but the intake decreased during the last part of lactation. Food intake regulation predominantly involves the recruitment of a variety of peripheral satiety systems that attempt to decrease the central feeding command system. Key words and growth of ratsThe increase of food intake during a normal lactation period in rats is the result of high energy requirements associated with the process of milk synthesis. The increased meal frequency during the daytime in the second and third postpartum weeks shows that at extremely high rates of energy expenditure, rats are capable of changing their feeding pattern (1). When lactating rats are subjected to severe malnutrition or offered imbalanced diets (low-protein-high-energy) that suppress food intake, milk production may be impaired due to metabolic changes including muscle protein degradation (2). The study of malnutrition during the lactation period shows that a decrease in food intake involves gastrointestinal and neural regulation.The purpose of the present study was to determine the alterations in food intake, maternal weight and litter growth during lactation when the dams were exposed to