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Why You're Fat

When You Eat Is Why You're Fat

Do you sometimes wait to eat meals? It’s not helping your waistline.

At this point, it’s practically conventional wisdom: If you skip breakfast, you’re going to have trouble losing weight, probably because you overeat later in the day (the Mayo Clinic offers a handful of other reasons why). A new study in the International Journal of Obesity takes the notion of timing and weight loss even further, claiming that when you eat meals throughout the day affects how easily you drop pounds.

The study, performed by researchers from Brigham and Women’s Hospital, the University of Murcia, and Tufts University, split 420 overweight participants into groups of early and late eaters. All of the participants followed a weight-loss diet, but half had lunch before 3 p.m., and half had lunch afterwards. It’s culturally important that the study focused on lunch; all the participants lived in Spain, where it’s the main meal of the day (and where 40% of the day’s calories are eaten).

Even though diet, energy intake, estimated energy expenditure, appetite hormone levels, and sleep duration were basically the same for all participants, the people who ate late lunches lost less weight—and lost it at a slower rate, too. The participants dropped weight at the same pace for the first five weeks of the 20-week study, but after that, those eating later saw their weight loss sputter to a halt. By the end of the study, they had lost 22% less weight than the earlier eaters.

The study summary points out that the later eaters often skipped breakfast and had higher insulin resistance, but not enough to explain the dramatic results.

And so, the authors conclude, "Eating late may influence the success of weight-loss therapy. Novel therapeutic strategies should incorporate not only the caloric intake and macronutrient distribution—as is classically done—but also the timing of food." In many parts of the world where dinner is the main meal of the day, eating earlier isn’t so easy. But for anyone serious about weight loss, it’s worth considering how timing might affect you.

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