Ask the Doc

When To Eat

Does it matter what time of day you eat?

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Depends on whom you ask. The American Dietetic Association would say no, but if you ask me, I’d definitely say yes!

Several recent studies, as well as a classic one from the ’70s, support the idea that mealtimes do matter – a lot. Most recently, researchers at Brigham and Women’s Hospital – in collaboration with Tufts University in Boston and the University of Murcia in Spain – ran a 20-week weight-loss study in Spain, where the biggest meal of the day is typically eaten around 3 pm. All participants followed the same Mediterranean-type diet plan, all slept for the same number of hours and the hunger hormone levels were comparable. Half the folks ate their heartiest meal around 3 pm or earlier, while half ate theirs after 3 pm. Participants who ate later in the day lost 22% less weight than those who ate earlier.

This is hardly the first time research has shown an effect of meal timing. A study at the Salk Institute for Biological Studies showed that mice that were limited to an eight-hour feeding period each day were much healthier (and weighed less) than mice that were allowed to eat freely anytime at all, and this was true regardless of what they actually ate. Half the mice in the study ate high-fat diets while the other half ate low-fat diets, but it didn’t matter; the mice restricted to eight hours a day gained less weight than the mice that ate at any time they pleased. And another animal study, at Northwestern University, allowed mice to eat as much weight-gaining food as they wanted, but one group ate only during the day while the other group ate only at night (when they would normally be sleeping). The day eaters gained about 20% of their initial weight, but the night eaters ballooned – gaining more than twice as much weight (a 48% increase!).

Military studies dating back to the ’70s show that men who are given an identical 2,000-calorie meal at different times of the day had their weight significantly impacted. Those who ate the heftier meal at breakfast didn’t gain weight, but those who ate the same meal at night did.

My best advice: Follow the old rule to eat breakfast like a king, lunch like a prince and dinner like a pauper. The research shows that the time you do eat truly does make a difference.