Dynamics of breast tumor incidence, tumor volume and serum metabolic hormones in calorie restricted rats.

Reports of the effects of calorie restriction on tumors after the tumor has developed are uncommon and limited to a few tumor types. We investigated the effects of calorie restriction on tumor growth in breast cancer after tumor growth had progressed. We used the N-nitroso-N-methylurea (NMU) induced breast cancer model in rats. In addition to a healthy control group (C), rats with 10 - 12 mm tumors were divided into three groups: cancer control group (CC), alternate day feeding group (ADF) and calorie restriction group (CR-50%). At the end of the experimental period the volume of tumors was decreased in the CR-50% group compared to the CC group. Serum adiponectin concentrations for the C and ADF groups were higher than for the CC group. All tumors of the CR-50% group were benign. The highest incidence of malignant and invasive tumors occurred in the CC group. A 50% calorie restriction appears to be an effective dietary intervention for advanced tumors.