Woman holding bottle of YakultAs if we weren't already confused enough about the pros and cons of probiotic drinks, scientists now say the tiny yoghurt drinks could help to combat weight gain.

US researchers have discovered that there are nasty little bugs living in our stomachs that could be causing us to get fat.Apparently, these naughty bacteria thrive on junk food, making weight gain even greater so the notorious "friendly" bacteria contained in drinks such as Yakult could help us to avoid piling on the pounds.

The research team at Washington University in Missouri, "transplanted" bugs, more usually found in the human gut, into mice.

They soon discovered that junk food triggered an alteration in the make-up of the bugs, with some thriving and others struggling to survive.

Taking the stomach bugs from mice being fed fatty foods and injecting them into lean mice revealed that even a low-fat diet couldn't prevent an expanding weight problem.

It is thought that the bugs that thrive on junk food affect the metabolism, leading to more fat being stored.

But probiotic drinks could, in future, be used to boost numbers of those happy little bugs who prefer a healthy diet, thereby keeping us trim – now that is what we'd call a friendly bacteria.

The study was published in the journal Science Translational Medicine reports.