The bacteria you have in your intestines may help determine your weight, according to 2 new studies, one human, and one in mice.

Gastric bypass surgery can help people to lose 65% to 75% of their excess weight.  These surgeries have also been shown to change the balance of the bowel bacteria. Is some of this weight loss due to the change is bowel bacteria? If so, perhaps a treatment less invasive than bypass surgery could help people lose weight. 

Earlier studies have shown that the microbiota of an obese person changed significantly after the surgery, becoming more like that of someone who was thin. This study was to see if the bowel flora change had weight loss effects of its own. 

Dr. Lee M. Kaplan, director of the obesity, metabolism and nutrition institute at the Massachusetts General Hospital, is an author of the study published Wednesday in Science Translational Medicine.

The researchers took 3 groups of mice, one group got the bypass surgery, the other 2 groups got a sham surgery.  One sham group was kept on the rich food, while the other was put on a weight-loss diet.

In the bypass mice, the microbial populations quickly changed, and the mice lost weight. In the sham group, the microbiota did not change much — even in those on the weight-loss diet.

Next, the researchers transferred intestinal contents from each of the groups into other mice, which lacked their own intestinal bacteria. The animals that received material from the bypass mice rapidly lost weight; stool from mice that had the sham operations had no effect.

Exactly how the altered intestinal bacteria might cause weight loss is not yet known, the researchers said

                                Who knows, perhaps the next weight loss pill will be a probiotic!