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Scientists at the Salk Institute found that mice lacking the biological clocks thought to be necessary for a healthy metabolism could be protected against obesity and metabolic diseases by having their daily access to food restricted to a 10-hour window. The health problems associated with disruptions to animals’ 24-hour rhythms of activity and rest which in humans is linked to eating for most of the day or doing shift work can be corrected by eating all calories within a 10-hour window.
Restricting food intake to 10 hours a day, and fasting the rest, can lead to better health. Every cell in mammals’ bodies operates on a 24-hour cycle known as the circadian rhythm- cellular cycles that govern when various genes are active. For example, in humans, genes for digestion are more active earlier in the day while genes for cellular repair are more active at night.
Mice allowed 24-hour access to a high-fat diet became obese and developed a slew of metabolic diseases including high cholesterol, fatty liver and diabetes. But these same mice, when restricted to the high-fat diet for a daily 8- to 10-hour window became lean, fit and healthy. Keeping the mice in better sync with their cellular clocks by eating most of the calories when genes for digestion were more active.
To test whether time-restricted eating could benefit these “clock-less” mice, researchers put mice on one of two high-fat diet regimes: one group had access to food around the clock, the other had access to the same number of calories only during a 10-hour window. As the team expected, the group that could eat at any time became obese and developed metabolic diseases. But the group that ate the same number of calories within a 10-hour window remained lean and healthy despite not having an internal “biological clock” and thereby genetically programmed to be morbidly sick. As human age, the circadian clocks weaken. This age-dependent deterioration of circadian clock parallels the increased risk for metabolic diseases, heart diseases, cancer and dementia.