A clinical trial demonstrated that a diet involving cycles of short-term, severe calorie restriction—a fasting-mimicking diet—can be safe, feasible, and may boost the antitumor activity of standard anticancer therapies. The study in cancer patients receiving different standard-of-care therapies found that cyclic fasting resulted in reduced blood glucose and growth factor concentrations, lower levels of peripheral blood immunosuppressive cells, and enhanced intratumor T-cell infiltration.