The tummy bugs that make you a yo-yo dieter

YO-YO dieters may struggle to stay slim due to a lack of diversity in gut bacteria, a study found.

It may also explain why obese people fight to keep weight off after a successful diet.

A balanced ‘community’ of beneficial bacteria in the stomach has been found to fight the flab.

In tests, losing weight led to more diverse bacteria associated with healthy weight levels. But in obese people who lost three stone, their bugs partly reverted to their former unhealthy states.

The finding – which has not been fully explained – may be a reason why diets can fail to work after a while in some individuals.

Certain bacteria are better at extracting energy from food, with surplus amounts converted to fat. It is thought that reducing levels of this type and increasing others could help stave off obesity and diabetes.

German researchers from University Hospital Schleswig-Holstein in Kiel put 18 obese adults on a diet of 800 calories per day for

‘Low-calorie diets aren’t enough’

three months and tracked how much weight they lost.

They also measured sensitivity to insulin, as well as gut bacteria diversity. They then tracked the same factors during a weight-maintenance diet for a further three months – and compared them to a control group.

The bacteria in the guts of the obese dieters had become more diverse at the end of their first three months. But the diversity was not sustained in the second phase. This was despite the dieters losing an average of just over three stone.

One limitation of the study is that the medications patients may have been taking were not accounted for, which could have an impact on bacteria diversity.

Dr Matthias Laudes, lead author of the study, said: ‘Anti-obesity campaigns often recommend low-calorie diet programs.

‘However, our work shows that this is not making enough of a long-term change in obese people’s gut bacteria.’