Many studies have found that restricting calorie intake extends the lifespan of animals ranging from worms and flies to mice and primates, by improving glucose regulation, lowering blood pressure, and reducing weight and inflammation. A new longitudinal study that followed hundreds of mice over their entire lifespans has found that, besides consuming less calories, eating only during their most active time of day substantially extended the lifespan of mice on reduced-calorie diets.
To unravel the effects of calorie intake, fasting, and circadian rhythms on longevity, researchers from the Howard Hughes Medical Institute (HHMI) undertook an extensive four-year experiment. Hundreds of mice were provided food through automatic feeders, which allowed the scientists to control when and how much each mouse ate for its entire lifespan. While some of the mice were allowed to eat as much as they wanted, others had their calorie intake restricted by 30 to 40 percent. Moreover, those on calorie-restricted diets ate on different schedules.
The experts found that the mice fed the low-calorie diet at night, over either a two-hour or 12-hour period, lived the longest. Combining a reduced-calorie diet with a nighttime eating-schedule added, on average, an additional nine months to the animals’ typical two-year lifespan. While a reduced-calorie diet alone extended the animals’ lives by 10 percent, feeding mice this diet only at nighttime, when they were most active, extended their lifespan by 35 percent.
As animals age, genes linked to inflammation tend to become more active, while genes that help regulate the metabolism become less active. The study results suggest that calorie restriction, particularly when timed to the mice’s active period at night, helped offset these genetic changes as mice aged.
According to Rafael de Cabo, a Gerontology researcher at the National Institute of Aging in Baltimore, this study “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.”
Scientists hope that better understanding how calorie restriction affects the body’s internal clocks as we age will help find new ways of extending the lifespan of humans too. This could happen through either calorie-restricted diets, or drugs that mimic those diets’ effects.
The study is published in the journal Science.