This clinical trial compares two different weight-loss programs, daily continuous calorie energy reduction (CER) versus (vs.) 5:2 intermittent fasting (IF), in preventing progression of kidney (renal) cancer among patients with one or more small renal masses (SRM) undergoing active surveillance (AS). Kidney cancer patients tend to have changes in metabolism that may increase body weight, but weight-loss strategies that work for best for these patients are unknown. The CER program requires a set daily limit for calories. The IF program requires fasting for 2 days a week and normal eating for the remaining 5 days. Both will include self-monitoring with interventionist feedback. This trial may help researchers determine whether the IF program works better than the CER program in improving weight loss, physical health, and/or reducing the risk of kidney cancer progression among patients with small renal masses undergoing AS