One problem with dieting is that when you give your body less energy to operate, it adapts to use less energy, which can slow weight loss. A way to get around that problem, a new study suggests, may be intermittent dieting—taking a two-week break for "regular" eating between bouts of dieting may actually improve weight loss.
The biological phenomenon that can lead to plateaus in weight loss (and trouble keeping the weight off) is something called "adaptive thermogenesis." When the body gets less energy than it's used to, it responds by lowering what's known as the "resting energy expenditure," the amount of energy your body uses simply to keep itself going. Since the amount of energy your body uses is tied to your weight and composition, you'd expect to use less energy as you slim down.
But research shows that during dieting—which is, remember, providing less food than your body is used to—resting energy expenditure decreases even more than would be expected simply due to weight loss. Adaptive thermogenesis is the change in biological and behavioral processes that lowers your resting energy expenditure. In other words, when you eat less, your body sheds pounds, yes, but then starts slowing its energy use to survive.
"This 'famine reaction,' a survival mechanism which helped humans to survive as a species when food supply was inconsistent in millennia past, is now contributing to our growing waistlines when the food supply is readily available," Nuala Byrne, who led the study with a team of collaborators from Queensland University of Technology and the University of Sydney, said in a statement.
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Researchers thought avoiding the famine reaction might improve overall weight loss. So they asked two groups to participate in a 16-week diet that cut their calorie consumption by a third. One group powered through the diet for the full 16 weeks; the other dieted for two weeks, then took two weeks of regular eating to maintain a stable weight, then returned to the lower-calorie diet for two weeks. That cycle lasted for 30 weeks, for 16 weeks of intermittent dieting.
Alternating dieting with "rest periods" of regular eating produced better results. The intermittent dieters lost more weight than their constant-dieting peers and had better success keeping it off after six months post-diet. On average, they had shed 8 kilograms (about 17 pounds) more at the six-month check-in.
Byrne noted that while the research suggests intermittent dieting can be more successful than constant dieting, it doesn't support diets that rely on more rapid fast-feast cycles. "There is a growing body of research which has shown that diets which use one to seven day periods of complete or partial fasting alternated with ad libitum food intake [eat what you want], are not more effective for weight loss than conventional continuous dieting," she said.
As always, more research is needed. But the preliminary results indicate that taking a break from dieting—once your body shifts into energy conservation mode—can lead to better overall results. If so, it's a good example of knowing when not to fight your body.
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