Yo-yo dieting might cause extra weight gain

December 5, 2016, University of Exeter
This is an image of a weight scale. Credit: CDC/Debora Cartagena

Repeated dieting may lead to weight gain because the brain interprets the diets as short famines and urges the person to store more fat for future shortages, new research by the universities of Exeter and Bristol suggests.

This may explain why people who try low-calorie diets often overeat when not dieting and so don't keep the weight off.

By contrast, people who don't diet will learn that food supplies are reliable and they do not need to store so much fat.

The study, published in the journal Evolution, Medicine and Public Health, is based on observations of animals such as birds.

Animals respond to the risk of by gaining weight, which is why garden birds are fatter in the winter when seeds and insects are hard to find.

The authors studied a mathematical model of an animal that knows whether food is currently abundant or limited, but does not know when things will change, so must learn about the changeability before deciding how fat to be.

The model shows that if food supply is often restricted (as it is when dieting) an optimal animal - the one with the best chance of passing on its genes - should gain excess weight between food shortages.

Dr Andrew Higginson, Senior Lecturer in psychology at the University of Exeter, says: "Surprisingly, our model predicts that the average weight gain for dieters will actually be greater than those who never diet.

"This happens because non-dieters learn that the food supply is reliable so there is less need for the insurance of fat stores."

With more and more people becoming obese, scientists are looking for evolutionary reasons to explain why many find it hard to resist overeating.

Humans evolved in a world where food was sometimes plentiful and sometimes scarce - and in the latter case those with more fat would be more likely to survive.

Today, people can get into a vicious cycle of weight gain and ever more severe diets - so-called yo-yo dieting - which only convinces the brain it must store ever more fat.

The researchers' model predicts that the urge to eat increases hugely as a diet goes on, and this urge won't diminish as weight is gained because the brain gets convinced that famines are likely.

"Our simple model shows that does not mean that people's physiology is malfunctioning or that they are being overwhelmed by unnaturally sweet tastes," says Professor John McNamara, of the University of Bristol's School of Mathematics.

"The brain could be functioning perfectly, but uncertainty about the triggers the evolved response to gain weight."

So how should people try to lose weight?

"The best thing for weight loss is to take it steady. Our work suggests that eating only slightly less than you should, all the time, and doing physical exercise is much more likely to help you reach a healthy weight than going on low-calorie diets," Dr Higginson says.

Explore further: Why frequent dieting makes you put on weight – and what to do about it

Related Stories

Why frequent dieting makes you put on weight – and what to do about it

November 25, 2016
People who regularly go on diets tend to lose weight initially but bounce back and even gain weight after stopping the regime. This phenomenon – dubbed yo-yo dieting – is associated with changes in metabolism and is one ...

New research shows dieting success may be hardwired into the brain

October 25, 2016
A new research paper, by Chen et al in Cognitive Neuroscience, studied the connections between the executive control and reward systems in the brain, and discovered the ability to self-regulate a healthy body weight may be ...

Dieting approaches may not be effective for weight loss, according to research

August 5, 2016
Weight control attempts by middle-aged New Zealand women are not linked with change in weight three years later, according to new University of Otago research.

Lessons learned from 'The Biggest Loser' study

August 1, 2016
Much media attention was given to a recent Obesity study that found that metabolism remained suppressed even when participants in "The Biggest Loser" television series regained much of the weight they lost while dieting. ...

Recommended for you

Bariatric surgery prolongs lifespan in obese

January 16, 2018
Obese, middle-age men and women who had bariatric surgery have half the death rate of those who had traditional medical treatment over a 10-year period, reports a study that answers questions about the long-term risk of the ...

Evening hours may pose higher risk for overeating, especially when under stress, study finds

January 16, 2018
Experiments with a small group of overweight men and women have added to evidence that "hunger hormone" levels rise and "satiety (or fullness) hormone" levels decrease in the evening. The findings also suggest that stress ...

Sugar-sweetened drinks linked to overweight and obesity in children, adults: Analysis of new studies

December 23, 2017
A new review of the latest evidence on sugar-sweetened beverages (SSBs)- which includes 30 new studies published between 2013 and 2015 (and none of them industry sponsored) - concludes that SSB consumption is associated with ...

As income rises, women get slimmer—but not men

December 21, 2017
(HealthDay)—A comprehensive survey on the widening American waistline finds that as paychecks get bigger, women's average weight tends to drop.

Policy and early intervention can curb obesity rates

December 18, 2017
More information and emphasis on dietary lifestyle changes that prevent obesity, and its comorbidities, have not reduced the rise in obesity in U.S. adults and adolescents, according to a recent study in the New England Journal ...

Warning labels can help reduce soda consumption and obesity, new study suggests

December 15, 2017
Labels that warn people about the risks of drinking soda and other sugar-sweetened beverages can lower obesity and overweight prevalence, suggests a new Johns Hopkins Bloomberg School of Public Health study.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.