Study finds it is better not to diet than to yo-yo diet

L-R: Dr Stephanie Simonds and Professor Michael Cowley.

It has long been suspected that ‘yo-yo’ dieting is ineffective in reducing body weight in the long run but little is known about its effect on health. Now Monash University’s Biomedicine Discovery Institute (BDI) scientists have conducted a study confirming that frequent on-off dieting not only makes diets less effective but could potentially increase the risk of diabetes.

Yo-yo dieting or ‘weight cycling’ occurs when someone starts a diet with the aim of losing weight but finds themselves once again consuming higher calorie foods and putting on body fat within a few weeks, initiating another bout of (inevitably unsuccessful) dieting. Athletes such as boxers and martial artists often enlist it to ‘cut weight’ for a fight after extended periods of plentiful caloric intake.

In a study recently published online in the journal Physiology & Behavior, Monash BDI researchers created a scenario in mice to mimic recurrent dieting in humans. They compared three groups: mice fed a low-calorie diet; those fed a high-calorie diet; and mice put on a diet cycle (four cycles consisting of two weeks high calorie then two weeks low calorie diet).

They found that the yo-yo mice:

  • were just as obese after four diet cycles as the mice fed an exclusively high-calorie diet,
  • had a lower metabolic rate than mice only fed high-calorie food, decreasing their energy expenditure,
  • were less physically active than mice only fed a high-calorie diet, and
  • were increasingly driven to eat high-calorie food with each successive diet cycle, and regained weight at a quicker rate each time.

The study also found that the yo-yo diet mice had a worse glucose tolerance than mice fed an exclusively high-calorie diet. Glucose tolerance is a measure of the body’s ability to absorb glucose from the blood into tissues following a meal. Impaired glucose tolerance is a risk factor for type-2 diabetes.

Lead author Professor Michael Cowley concluded that, “frequent dieting makes diets less effective and causes reduced energy expenditure, meaning that you have to continue dieting indefinitely in order to maintain a low body weight.”

“However, what is of more concern is that diet-cycled mice had poor blood glucose control – worse than mice fed high calorie diet continuously. This indicated that yo-yo diet mice are actually at a higher risk of diabetes that high calorie-fed mice,” Professor Cowley said.

“This study demonstrates that yo-yo dieting is actually worse than no dieting at all,” he said.

Professor Cowley said it was important to inform people about yo-yo dieting.

“We exist in a world where people are more and more conscious of their weight and of getting that ‘body for the beach’,” he said.

“I think yo-yo dieting is training the body to better prepare for starvation. A healthier strategy would be to encourage people not to be so drastic in their dietary interventions, to think about making smaller but lasting changes.”

The other authors on this paper were Dr Stephanie Simonds and Dr Jack Pryor.

This research was supported by the NHMRC.

Read the full paper in Physiology & Behavior titled Repeated weight cycling in obese mice causes increased appetite and glucose intolerance.