Health outcomes of interest are changes in weight and metabolic parameters associated with type 2 diabetes, cardiovascular disease, and cancer. Because much of the data on intermittent fasting is from research in animal models, we briefly summarize key rodent studies and reviews. The overall objective of this paper is to provide an overview of intermittent fasting regimens ( Table 1) and summarize the evidence on the health benefits of intermittent fasting with a focus on human intervention studies. However, scientific evidence for the health benefits of intermittent fasting in humans is often extrapolated from animal studies, based on observational data on religious fasting (particularly Ramadan), or derived from experimental studies with modest sample sizes. 2 Dozens of books promote various fasting dietary patterns and the web offers hundreds of fasting-related sites. For example, in 2013, Mosley and Spencer published a best-selling book titled “The Fast Diet,” which touts the benefits of restricting energy intake severely for two days a week while eating normally the rest of the week. 1 Renewed interest in fasting regimens is evidenced by a plethora of popular press publications and diet recommendations. Books on ethnology and religion describe a remarkable variety of fasting forms and practices. Senger, MD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, Elena Martínez, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, (858) 822-3638, Villaseñor, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, (858) 822-6827, of voluntary abstinence from food and drink (i.e., intermittent fasting) has been practiced since earliest antiquity by peoples around the globe. Loki Natarajan, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, (858) 822-4763, M. Hartman, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, (858) 534-9235 Gallo, PhD, Department of Psychology, San Diego State University, San Diego, CA, USA, (619) 594-4833, J. LaCroix, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, (858) 822-0627, Marinac, BA, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Graduate School of Public Health, San Diego State University, San Diego, CA, USA, C. Sears, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Medicine, Division of Endocrinology and Metabolism, University of California, La Jolla, California, USA, (858) 534-8898, Z. Laughlin, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, (858) 822-2416, D. Patterson, PhD, Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA, Department of Family & Preventive Medicine, University of California, San Diego, La Jolla, CA, USA, 3855 Health Sciences Drive, La Jolla, CA 92093, (858) 534-2563, A.