Fasting increases health and lifespan in male mice

At a Glance Long periods of fasting between meals helped male mice live longer and healthier lives, regardless of the content of their diets.

More studies are needed to confirm these results and understand how different fasting periods may impact health.

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Studies have suggested potential health benefits from long-term calorie restriction. In long-term calorie restriction, average daily caloric intake is kept below what is typical or habitual, but without malnutrition or deprivation of essential nutrients. Calorie restriction can be achieved through simply eating less overall, or through specific periods of fasting.

One decades-long study in rhesus monkeys found an extension of lifespan with calorie restriction. However, another did not. Differences between those two studies—including the type of food used—made comparisons difficult.

Researchers from NIH’s National Institute on Aging (NIA), led by Dr. Rafael de Cabo, wanted to better understand if the type of food eaten, and when it is eaten, alters how calorie restriction affects the body. They divided almost 300 male mice into two diet groups. One group was given a diet low in sugar and based more on whole foods. The other group's diet was higher in sugar and more processed.

Within these two groups, the researchers divided the mice into three feeding regimens. One had access to a food dispenser at all hours of the day (ad libitum, AL). A calorie restricted (CR) group received 30% less food than the AL group, placed into their cage once a day at the same time. A meal fed, or MF, group was given the same amount of food as the AL mice on average, but were fed only once a day.

The mice were monitored over the course of their natural lives. Mice that died were examined for evidence of disease, including cancer and liver damage. The results were published on September 6, 2018, in Cell Metabolism.

The researchers had expected that mice eating the whole foods-based diet would have a survival advantage when calorie restricted. But this is not what they observed. Diet composition did not affect health and lifespans. However, the periods of fasting did.

Mice in the MF groups quickly learned that they would not have 24-hour access to food and developed the habit of eating quickly. Mice in the CR groups also finished their smaller meals rapidly. Therefore, the mice in these groups had extended periods of time without food.

Compared with mice in the AL groups, mice in the MF groups lived about 11% longer, even though their total food intake and body weights were similar. Mice in the CR group lived about 28% longer. Mice in the CR and MF groups also developed disease later than mice in the AL groups.

“Increasing daily fasting times, without a reduction of calories and regardless of the type of diet consumed, resulted in overall improvements in health and survival in male mice. Perhaps this extended daily fasting period enables repair and maintenance mechanisms [in the body] that would be absent in a continuous exposure to food,” Cabo says.

Studies in female mice, as well as in other animals, are needed to confirm these findings. More work will also be needed to explore how different lengths of fasting impact health. Finally, the impact of fasting on human health may differ in important ways.