Study shows yo-yo dieting fails to work

YO-YO dieting is not a good way to lose weight, and may make people hungrier, less active and drive up their risk of type two diabetes.

Research by Monash University’s Biomedicine Discovery Institute found bouts of calorie restriction make subsequent diets less effective.

Lead author Professor Michael Cowley said most diets, whether ketogenic, low-fat, intermittent fasting or Palaeolithic, involved cutting calories.

In his study, some obese mice were fed high-calorie diets as others were made to yo-yo diet for two weeks at a time.

After four bouts of yo-yo dieting, the mice were just as fat as those that stuck to their normal diet. The yo-yo dieting mice regained weight they lost faster with each successive diet.

Worryingly, the dieters also had worse blood glucose tolerance, indicating a higher risk of developing type two diabetes.

“Each time we put them back on the low-fat diet they lost less weight so dieting became less effective,” Prof Cowley said. “When we put them back on the normal diet they were really hungry and rapidly regained the weight they lost, and went back up to the weight that the animals that stayed on the high-calorie diet.

“So in addition to training them to not lose weight on a diet, we taught them to overconsume food.”

Professor Margaret Morris, from the University of New South Wales, said the study in the journal Physiology and Behavior showed the obese mice that cycled on and off the diet showed signs of being metabolically compromised.

Her team did a similar study on healthy rats that yo-yo dieted for 16 weeks and found they weighed more, had higher leptin levels and fat mass.

Animal studies were important to understand mechanisms, she said, but it was difficult to translate results directly to humans.

“I think a key focus needs to be preventing obesity because once you are compromised, it’s very hard to come back from that,” Prof Morris said.

Prof Cowley said the message for people trying to lose weight was to make smaller, less drastic changes.

“It’s pretty clear that yo-yo dieting, this boom and bust way of dealing with your body, is actually worse than not dieting at all,” she said.