Fasting Linked to Living Longer

Fasting between meals could boost health and prolong life, according to a study on mice.

And the animals appeared to reap the benefits of fasting regardless of their diet or how many calories they consumed.

To investigate the effects of fasting, the researchers split 292 male mice into two groups. One group was assigned a diet low in purified sugars and fat, but higher in protein and fat than the other. The mice were then divided again into three groups according to feeding times.

The first group could eat whenever they wanted. The second were fed 30 percent less calories per day than the first, while the third group was given a single meal that equaled the diet of the round-the-clock group.

The researchers measured health and lifespan by noting when mice naturally died, and examining their bodies after death.

Both mice who were meal-fed and had restricted calories had better health overall, lived longer, and had fewer signs of age-related damage to their internal organs. But the calorie-restricted mice also had better fasting glucose and insulin levels.

Researchers at the National Institute on Aging (NIA) at the National Institutes of Health, the University of Wisconsin-Madison, and the Pennington Biomedical Research Center, Baton Rouge, Louisiana, collaborated on the study published in the journal Cell Metabolism.

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Dr. Rafael de Cabo, chief of the Translational Gerontology Branch of the National Institute of Aging Intramural Research Program told Newsweek: "For almost a century we knew that reducing the caloric intake of laboratory animals we could extend their life, preserve their functions and health.

"This study unveils that it is not only the calories that matters, the time that the animals spend fasting seems to be very important. We knew of the beneficial effects of fasting on health for a while, but this is the first study that shows that prolonged daily fasting times extends lifespan independent of calories and type of diet.

He said in a statement: "Perhaps this extended daily fasting period enables repair and maintenance mechanisms that would be absent in a continuous exposure to food."

But as the study was performed in mice, researchers will need to replicate their study in humans to uncover whether we experience the same effects.

Still, the researchers said their findings lay the groundwork for future studies into whether time-restricted eating patterns could help humans keep a healthy weight, and avoid age-related metabolic diseases.

In recent years, evidence in animals has been piling up in favor of fasting. But the concrete evidence to support their benefits in humans remains sparse.

James Catterson of the Institute of Healthy Ageing at University College London, who was not involved in the study, told Newsweek: "This large study is significant as it shows that daily fasting without caloric restriction can have significant benefits on health and longevity.

"What's new about this study is that diet composition doesn't seem to affect the beneficial effects of fasting. This might be good news for humans who undergo dietary fasting (especially the 16:8 diet), as it means that it might not matter what they eat between fasts."

But he cautioned the study was performed in mice. "Though the results are exciting, humans trials have yet to be performed with this regimen. But it does add to the growing body of evidence that meal timing and or frequency are just as important as diet content."

In a separate interview with Newsweek, Catterson said there is more data in animals pointing to the advantages of fasting.

"There are also many studies that either report no overall effect or sometimes the opposite. And this is where it gets a bit murky, as it is very difficult to put proper controls in place when performing studies to do with nutrition," Catterson said.

He concluded: "So far, the consensus seems to be 'let's wait until more rigorous studies, with larger sample sizes that adjust for confounding lifestyle behaviors, have been performed before we conclude anything prematurely."

This article has been updated with commment from Dr. Rafael de Cabo and Dr. James Catterson.