Near-fasting for 5 days a month reduces body fat, study finds
Diet smarter, not longer.
Slashing your food intake for just five consecutive days a month can yield a bounty of health benefits, according to a new study led by researchers from the University of Southern California. This briefer approach to caloric restriction, a severe form of dieting, challenges previous research that dieters might need to tighten their belts as often as twice a week to see positive effects.
The team fed mice and humans a “fasting-mimicking diet,” a low-calorie, high-nutrition plan designed to trick cells into thinking they were fasting. The faux fasting periods lasted a few days and were followed by cycles of eating as much and as often as subjects wanted. The results appear online June 18 in Cell Metabolism.
Biogerontologist and study coauthor Valter Longo says the results show “that you can have a smart diet, a diet that can push all the right buttons,” without the severity seen in other caloric-restriction regimens.
Mice lived about 11 percent longer (although this trend disappeared in very old mice), had fewer indicators of inflammation and cancer and saw a host of other benefits. Most notably, their brains grew more nerve cells, even when elderly.
The human trial was small —just 19 dieters —and short, lasting three months. Mice ate the diet for roughly half their lives for eight days a month rather than five.
In many studies, caloric restriction has been shown to extend life span and improve health in certain organisms, but other research has produced conflicting results (SN: 1/24/15, p. 6, SN Online: 7/30/14), and scientists still aren’t sure how it works. But this study hints that the rest periods between bouts of dieting, not the time spent cutting calories, may play an important role in nerve cell growth in mice, says Mark Mattson, a neuroscientist at the National Institute on Aging in Baltimore, Md., who wasn’t involved in the study. In his own research, Mattson has found that fasting can yield nerve cell regeneration in the mouse brain, but his mice endured a much stricter fasting regimen of little to no food every other day. He says this new study shows the importance of the refeeding and recovery periods. “That was new and very interesting.”
Editor's Note: This story was updated July 7, 2015, to clarify that most but not all of the researchers in the study were affiliated with the University of Southern California.
S. Brandhorst et al. A periodic diet that mimics fasting promotes multi-system regeneration, enhanced cognitive performance, and healthspan. Published online June 18, 2015. Cell Metabolism. doi: 10.1016/j.cmet.2015.05.012.
T. Saey. Hydrogen sulfide offers clue to how reducing calories lengthens lives. Science News Vol. 187, p. 6. Jan. 24, 2015.
T. Saey. For yeast life span, calorie restriction may be a wash. Science News online. July 30, 2014.
T. Saey. Meaty diets may raise risk of dying young. Science News Vol. 185, p. 6. April 5, 2014.
N. Seppa. Low-cal longevity questioned. Science News Vol. 182, p. 8. October 6, 2012.