If you begin to regain weight after gastric bypass surgery, talk to your doctor. You may have a sense of what's causing your weight gain. However, you may need a more thorough evaluation to determine what factors — medical, psychological, lifestyle — are involved in the weight gain.

You may have gained weight after gastric bypass surgery because of changes in your stomach and intestine that allow you to eat more and absorb more calories.

It's also possible that your diet and exercise habits have slipped, in which case you must typically lose the regained weight the old-fashioned way — both by reducing your calorie intake and increasing your physical activity.

In some cases, a second surgery to repair — or redo — a gastric bypass may be appropriate. This is especially true if the anatomy of your stomach and small intestine have changed, such as with a fistula (additional connection between the stomach and intestine).

However, a second surgery has an increased risk of complications, including infection, bleeding and leaks in the gastrointestinal tract. Because of these risks, gastric bypass surgery usually isn't redone if you regain weight because of poor diet or exercise habits.

Gastric bypass surgery can be an effective treatment for obesity, and most people do lose weight after the procedure if they are adequately prepared for the changes that are necessary. But you'll always be at risk of regaining weight, even years later.

To help reach your weight-loss goal and prevent weight regain, it's crucial to make lifestyle changes along with having gastric bypass surgery.