Another case against the midnight snack: Researchers tinker with a time-restricted diet in mice and find that it’s remarkably forgiving

A new study by researchers at the Salk Institute cautions against an extended period of snacking, suggesting instead that confining caloric consumption to an 8- to 12-hour period-as people did just a century ago-might stave off high cholesterol, diabetes and obesity.

The results, published December 2, 2014 in the journal Cell Metabolism, add to mounting evidence suggesting that it’s not just what we eat but when we eat it that matters to our health. Although the intervention has not yet been tested in humans, it has already gained visibility as a potential weight loss method-and, in mice, it may reveal what causes obesity and related conditions in the first place.

In 2012, Satchidananda Panda, a Salk associate professor, showed that mice which were fed a high-fat diet, but allowed access to that diet for only eight hours per day, were healthier and slimmer than mice given access to the same food for the whole day, even though the two groups consumed the same number of calories. The new study shows the benefits of time restriction is surprisingly more profound than initially thought and can reverse obesity and diabetes in animal models.

The authors demonstrated that time restriction better synchronizes the function of hundreds of genes and gene products in our body with the predictable time of eating.

“These days, most of the advice is, ‘You have to change nutrition, you have to eat a healthy diet,'” Panda says. “But many people don’t have access to healthy diets. So the question is, without access to a healthy diet, can they still practice time-restricted feeding and reap some benefit?”

Panda and his researchers, who study the body’s 24-hour rhythms, wanted to know how forgiving time-restricted feeding was.

In the new study, Panda’s group subjected nearly 400 mice, ranging from normal to obese, to various types of diets and lengths of time restrictions. They found that the benefits of time-restricted feeding showed up regardless of the weight of the mouse, type of diet and length of the time restriction (to some degree).

Regardless of whether their diets were high in fat, fat and sucrose or just fructose, mice that were given time restrictions of 9 to 12 hours-and consumed the same amount of daily calories as their unrestricted counterparts-gained less weight than the controls, researchers found.

In particular, variations in the time window in which the mice were allowed to eat a high-fat diet-including 9-, 10- and 12-hour periods-all resulted in similarly lean mice. For a 15-hour group, the benefits conferred by time restriction became more modest.

Researchers gave some of the time-restricted mice a respite on weekends, allowing them free access to high-fat