New York, May 8 (IANS): Want to live longer? Restrict your intake of calories and eat food at the right time to live a longer and healthier life, finds a study.

The study led by researchers at the Hughes Medical Institute in the US suggests that the body's daily rhythms play a big part in this longevity effect.

Eating only during their most active time of day substantially extended the lifespan of mice on a reduced-calorie diet, said Joseph Takahashi, an investigator at the Institute.

In the study, reported in the journal Science, the team examined hundreds of mice over four years and found that a reduced-calorie diet alone extended the animals' lives by 10 per cent. And feeding mice only at nighttime, when mice are most active, extended their life by 35 per cent.

That combo - a reduced-calorie diet plus a nighttime eating schedule - tacked on an extra nine months to the animals' typical two-year median lifespan.

For humans, an analogous plan would restrict eating to daytime hours, the team said.

The research helps disentangle the controversy around diet plans that emphasise eating only at certain times of day, said Takahashi, who is also a molecular biologist at the University of Texas Southwestern Medical Center.

Such plans may not speed weight loss in humans, but they could prompt health benefits that add up to a longer lifespan.

Recent years have seen the rise of many popular diet plans that focus on what's known as intermittent fasting, such as fasting on alternate days or eating only during a period of six to eight hours per day.

To unravel the effects of calories, fasting, and daily, or circadian, rhythms on longevity, Takahashi's team undertook an extensive four-year experiment. The team housed hundreds of mice with automated feeders to control when and how much each mouse ate for its entire lifespan.

Some of the mice could eat as much as they wanted, while others had their calories restricted by 30 to 40 per cent. And those on calorie-restricted diets ate on different schedules. Mice fed the low-calorie diet at night, over either a two-hour or 12-hour period, lived the longest, the team discovered.

Rafael de Cabo, a gerontology researcher at the National Institute on Aging in Baltimore says that the finding "is a very elegant demonstration that even if you are restricting your calories but you are not [eating at the right times], you do not get the full benefits of caloric restriction."

Takahashi hopes that learning how calorie restriction affects the body's internal clocks as we age will help scientists find new ways to extend the healthy lifespan of humans. That could come through calorie-restricted diets, or through drugs that mimic those diets' effects, he added.