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In my last chronobiology video, we learned that the exact same number of calories at breakfast are significantly less fattening than the same number of calories eaten at supper. But who eats just one meal a day?

What about just shifting our daily distribution of calories earlier in the day? Israeli researchers randomized overweight and obese women into one of two “isocaloric” groups, meaning each group was given the same number of total calories. One group was given a 700-calorie breakfast, a 500-calorie lunch, and a 200-calorie dinner; and the other group was given the opposite, 200 for breakfast, 500 for lunch, and 700 for dinner. Since they were all eating the same number of calories overall, the king-prince-pauper group should have lost the same amount of weight as the pauper-prince-king group, right? But no, the morning-slanted group lost more than twice as much weight, in addition to slimming about an extra two inches off their waistline. By the end of the 12-week study, the king-prince-pauper group lost 11 more pounds (19 pounds lost compared to 8 despite eating the same number of calories). That’s the power of chronobiology, the power of our circadian rhythms.

… 700 500 200 is 50 percent of calories at breakfast, 36 percent of calories at lunch and only 14 percent of calories at supper. That’s pretty skewed. What about 20 percent for supper instead, a 50 percent-30 percent-20 percent spread, compared to 20-30-50? Again, the bigger breakfast group experienced “dramatically increased” weight loss, about nine pounds different in eight weeks with no significant differences in overall calorie intake or physical activity between the groups.

Instead of 80 percent+ of calories at breakfast and lunch, what about 70 percent compared to 55 percent? Overweight “homemakers” were randomized to eat 70 percent of their calories at breakfast, a morning snack, and lunch, leaving 30 percent for an afternoon snack and dinner, or a more balanced 55 percent up through and including lunch. In both cases only a minority of calories were eaten for dinner. Would it matter if it was just 55 percent up through lunch or 70 percent? Yes, significantly more weight loss and slimming in the dietary pattern that was even more biased towards the morning.

“Stories about food and nutrition are in the news on an almost daily basis, but information can sometimes be confusing and contradictory. Clear messages should be proposed in order to reach the greatest number of people,” the researchers conclude. And one clear communication physicians could give is “If you want to lose weight, eat more in the morning than in the evening.”

Even just telling people to eat their main meal at lunch rather than dinner may help. Despite comparable calorie intakes, participants in a weight loss program randomized to get advice to make their main meal lunch, beat out those who instead were told to make their main meal dinner.

The proverb “Eat breakfast like a king, lunch like a prince, and dinner like a pauper” evidently has another variant: “Eat breakfast yourself, share lunch with a friend, and give dinner away to your enemy.” I wouldn’t go that far, but there does appear to be metabolic benefit to frontloading the bulk of your calories earlier in the day.

The evidence isn’t completely consistent, though. A review of dietary pattern studies questioned the role that reducing evening intake would facilitate weight loss, citing this study that showed the evening-weighted group did better than the heavy morning meal group. Perhaps that was because the morning meal group was given for breakfast “chocolate, cookies, cake, ice cream, chocolate mousse and donuts.” So, chronobiology can be trumped by a junk food methodology. Overall, the “what” is still more important than the “when.” Caloric timing may be used to accelerate weight loss but doesn’t substitute for a healthy diet. When he said there was a time for every purpose under heaven, Ecclesiastes probably wasn’t talking about donuts.

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