The weight loss is ‘modest’, say researchers, but it can be enough to prevent type 2 diabetes, for instance, especially if someone is already overweight.

In a review of 25 previously-published studies that tested the effectiveness of probiotics on more than 1,900 people, researchers from the Taizhou People’s Hospital in China found that taking probiotics reduced weight and people’s BMI (body-mass index) score, the standard measure of obesity.

The biggest loss of weight was seen in those who were taking several probiotics a day and for at least eight weeks.

Although it’s often been claimed that probiotics make our gut more efficient and so help us lose weight, it is a benefit that had never been firmly established, say the researchers. Probiotic supplements, which are often added to yoghurts, are also supposed to improve the immune system.