If obesity is linked to Americans' 24/7 lifestyles, would it help to reset the clock that dictates our eating? A new study suggests it would, and in ways that go well beyond weight alone.

Even with a diet high in fat and sugar, mice that had their "eating day" compressed into eight to nine hours and then fasted for the remainder of the day were less likely to become obese, says new research. Mice that observed a lengthy daily fast also suffered less systemic inflammation, fatty liver disease, worrisome cholesterol and metabolic disturbance than did mice that ate whenever they pleased.

The difference wasn't how much or what the mice ate: Mice kept on a daily fasting regimen ate the same fattening chow, and just as much of it, as did those who ate around the clock. The only difference was when they ate it — and how long they did without.

The study, published this week in Cell Metabolism, builds on the idea that our cells adhere to a sleep-wake cycle and process fuel differently at different times of the day.

Researchers at the Salk Institute for Biological Studies in the San Diego-area community of La Jolla subjected 392 male lab mice to a variety of feeding patterns and gauged the effects on a wide range of metabolic and physiological measures.

Compared with mice allowed to eat whenever they wanted, those who did all of their eating in nine hours a day gained only half as much weight, even though both groups consumed about the same number of calories.

The daily fasters also showed exercise endurance far superior to that of mice with no eating restrictions. They not only outran the chubby all-day eaters, they also left mice reared on normal, healthy chow in the dust.

A long daily fast also aided in weight loss among mice that were obese. Those switched from the eat-when-you-want mode to a 15-hour daily fast mode lost 5 percent to 12 percent of their body weight over three months, while the mice who continued to eat throughout the day saw their weight rise an additional 10 percent to 25 percent.

And mice that reaped the rewards of fasting could make an occasional dietary detour and still stay healthy.

"I wouldn't run out and start doing this in humans," said Kenneth P. Wright, director of University of Colorado at Boulder's sleep and chronobiology lab, who wasn't involved in the research. But "studying these effects in humans is certainly the next step," he said.

Time-restricted feeding is a potentially powerful behavioral intervention that "de-emphasizes caloric intake, hence making it an attractive and easily adoptable lifestyle modification," the Salk researchers wrote.


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