Here, we demonstrate that cycles of very low caloric intake either with AIN-93G chow (LCC) or a plant-based diet (FMD) were equally effective at delaying primary 4T1 tumor growth in young BALB/cJ females, a finding consistent with previous studies indicating that the growth of 4T1 breast cancer cells, contrary to other types of cancer6, is not affected by protein restriction and the consequent lowering of IGF-1. Here, IGF1 is linked to breast cancer.