Now scientists believe that the 'yo-yo effect', gaining weight after successfully dieting, may be caused by bacteria in our guts. While our body loses weight, the microbes living inside us used to a fatty diet remain for many months. And when they come across fatty foods again, they go into overdrive, making us pile on the pounds at an accelerated rate.
This effect could be reversed, scientists believe, by taking a drink containing high levels of the substances which are found naturally in fruit and vegetables.
These compounds – flavonoids - encourage our cells to 'burn' fat rather than storing it.
Although the research was in mice, scientists believe a similar mechanism may work in humans.
One of the flavonoid compounds, apigenin occurs in parsley, celery, celeriac, and chamomile tea. The other, naringenin, is present in grapefruit, oranges, tomato skin and water mint.
The new study carried out by Israeli researchers investigated how mice who became obese after a high fat diet, successfully lost weight after a normal diet.
But when they started eating fatty foods again, they regained at an 'accelerated' rate.
Key to the process was 'bad' bacteria in the gut reducing the levels of flavonoids in the gut, the scientists said.
Feeding the mice drink with very high levels of the flavonoids– more than can be absorbed by the gut bacteria - 'helped to curb post-dieting weight regain in mice'.
Eran Segal , co-author of the research said further research is needed before the same process works in humans.
