Anyone who has ever lost weight on a diet has probably experienced the crushing defeat of watching the pounds come rushing back when the dieting stops. A new study may have identified a specific gut bacterium responsible for post-dieting weight gain.

The research, published in Nature Metabolism, used ten short-term, low-calorie dieting routines to study how caloric intake affects weight loss and gain in mice. As expected, once the dietary restrictions were lifted, there was a massive increase in fat accumulation not seen in non-dieting mice.

Most importantly, weight gain was linked to the amount of fat absorbed by the gut post-diet, rather than the increase in caloric intake during the refeeding period.

To test the effects (if any) of nutrition on post-diet weight gain, the study gave one group of mice a high-protein diet and the other a regular-protein diet during the refeeding period. The high-protein diet prevented rapid fat gain and the mice in this test maintained some of their weight loss.

Further, the test found 50 percent more of the bacteria Lactobacillus in the guts of the mice with the regular-protein refeeding diet than those that consumed a high-protein diet.

To confirm the role of Lactobacillus in post-diet weight gain, study authors destroyed the bacteria with penicillin in the guts of mice. As predicted, the mice without the bacteria showed an overall reduced body fat accumulation after dieting.

What does all this mean for humans on weight-loss diets? After the diet ends, consuming a high-protein regime will help reduce weight gain and sustain desired results.