Nearly two-thirds of Americans are overweight or obese, and many struggle throughout their lives to try to control their calorie intake and body weight.

But now dieters have reason to hope for more effective weight-loss treatments thanks to results from a study published in the journal Science Translational Medicine.

Researchers found that patients who underwent gastric bypass surgery not only lost weight because their stomachs absorbed fewer calories, but also from a change in the balance of bacteria in their intestines that ramped up metabolism.

The findings should open the door to new studies of treatments designed to increase the proportion of good germs in our guts.

Because obesity can increase the risk for cognitive impairment, mood disorders, and low self-esteem, these new treatments may benefit a variety of mental health problems.