Fasting between meals can burn fat and improve metabolic health


Eating three meals per day- breakfast, lunch, and dinner- has become engrained in many cultures. Many hold the notion that regular and frequent eating is vital for health. Yet, new research suggests that eating the same total amount of food, but increasing the duration of fasting between meals may yield better health outcomes.

A recent study in Cell Metabolism found that mice fed just two meals per day, one in early morning and another in late evening, had decreased body fat but increased muscle mass relative to a control group that had continual access to food. Both groups ate the same number of calories, but the mice that fasted between meals had a higher metabolic rate. Fasting between meals prevented metabolic syndrome, a cluster of conditions that increase risk of cardiovascular disease and diabetes.

The researchers evaluated a wide range of cardiometabolic health effects in muscle, fat, and liver tissues. Interestingly, the physiologic effects of a meal after a long fast differed depending on whether the meal occurred in the morning or evening. For example, when the mice ate after their active period (in the morning, as mice are nocturnal) their levels of FGF-21, a protein associated with metabolically health and fat-burning effects, spiked. However, when mice ate after sleeping the physiologic benefits of fasting were less striking.

If these effects are conserved in people, eating less frequently might improve health even without eating less total calories. To optimize the beneficial effects of fasting, it might be best to fast while being active during the day and eat a larger meal at night.

As always, there are limits to the study. Only one genetic type of mouse was studied, so we do not know if these effects are specific to a certain genetic makeup or if genetically diverse individuals would also have similar health benefits. Moreover, the metabolic rate of mice is much higher than humans. If humans had the same metabolic rate as mice, we would need to eat ~25,000 calories/day to maintain our weight. So, it could be that eating twice per day for a mouse is more comparable to a human eating twice every few days. Regardless, it appears that the old adage of three meals per day may not always be correct.

Personally, I often skip lunch and sometimes both breakfast and lunch. For me, it’s more convenient than looking for food every couple hours and I feel more productive. However, I do know other people who are not fun to be around if they skip a meal. As with everything, there is individual variation. Perhaps give it a try and see how you feel.

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