A study exploring the role of cellular circadian rhythms in obesity shows that restricting eating to a 10-hour window provides protection from weight gain and metabolic diseases in mice lacking a circadian clock. The research, published in Cell Metabolism, suggests that people with abnormal circadian rhythms— from doing shift work, for example—can avoid adverse health impacts by adopting a time restricted eating plan.
In mammals, circadian rhythms are cellular cycles of 24 hours during which different sets of genes are active. For example, genes for digestion are more active in the day and genes involved in repair and recovery are activated at night. Previous research in mice with normal circadian clocks that were fed a high-fat diet showed that those on time-restricted feeding (TRF) for an 8 to 10-hour window were lean and healthy compared to mice allowed to free feed on the same diet for 24 hours. The results were attributed to eating times being aligned with their cellular clocks.
The current study used knockout mice that lacked a cellular clock. These “clock-less” mice are prone to metabolic diseases and the risk is escalated when fed a high-fat or sugary diet. The mice were again split into two groups, one allowed to eat a high-fat diet for all 24 hours and the other restricted to eating the same diet in a 10-hour period. As expected, the free feeding mice gained weight and developed metabolic disease. The mice on the TRF plan maintained a healthy weight and did not get sick, suggesting that limiting caloric intake to a smaller number of hours during the day provides protection against disease even without innate molecular clocks.
Our circadian clocks become less effective as we get older and, at the same time, we’re more susceptible to a number of diseases including cancer and metabolic syndrome. However, according to the researchers, making the simple change to our daily eating routine can go a long way toward remaining healthy and lowering the risk of disease. "Many of us may have one or more disease-causing defective genes that make us feel helpless and destined to be sick. The finding that a good lifestyle can beat the bad effects of defective genes opens new hope to stay healthy," says Satchidananda Panda, a professor in Salk's Regulatory Biology Laboratory and the senior author of the new paper.