Researchers at the University of Tasmania looked at the body’s ‘famine reaction’ to continued dieting, by studying obese men who took part in a 16-week diet that cut their calorie intake by a third.
One group stuck strictly to the diet for the entire four months, the other took a two-week break every two weeks but kept this up for 30 weeks in total, so that they also spent 16 weeks on a diet, just not continuously.
The group that dieted intermittently not only lost more weight but were also more successful at keeping the weight off. The intermittent dieters maintained an average weight-loss of 8 kilograms more than the continuous dieters over a six-month period after the trial ended.
Professor Nuala Byrne, who headed the study published in the International Journal of Obesity, said that the survival mechanism known as the famine reaction made continuous dieting less effective than intermittent dieting. That’s because our metabolism slowed when food intake was reduced, she explained, according to a report by Scimex.
“[It] helped humans to survive as a species when food supply was inconsistent in millennia past, [but] is now contributing to our growing waistlines when the food supply is readily available,” Byrne said.
She said, however, that the key to the intermittent group’s success appeared to be that they took a significant period – two weeks – off from the diet, because studies had shown that fasting diets, where the dieter cycles through days of normal eating and days of severely restricted food intake, were no more effective that continuous dieting.
“It seems that the ‘breaks’ from dieting we have used in this study may be critical to the success of this approach,” she said.
This article originally appeared on Starts at 60.