People who’ve undergone surgery to manage their obesity may lose more weight if they start exercising, a new study suggests.

More and more severely obese adults are turning to gastric bypass surgery in an effort to lose weight. The procedure, which restricts the amount of food a person can eat, can spur substantial weight loss and help control obesity-related conditions like diabetes.

However, while regular exercise is a well-known way to keep body weight in check, it has not been clear whether people who start exercising after gastric bypass fare any better than those who remain sedentary. The new study suggests that they do.

Researchers found that of 199 patients who underwent gastric bypass, those who became more active after surgery lost more weight over one year than those who remained relatively inactive.

In fact, the former group did as well as patients who were regularly active both before and after their gastric bypass surgery, the researchers report in the journal Obesity.

All of the study patients had undergone Roux-en-Y gastric bypass, in which a surgeon staples off the upper portion of the stomach to create a small pouch that restricts the amount of food a person can eat at one time. The surgeon also creates a bypass around the rest of the stomach and a portion of the small intestine, which limits the body’s absorption of food.

The weight-loss effects of the procedure itself are so “powerful,” it is notable that a lifestyle change may still make an important difference, noted lead researcher Dr. Dale S. Bond, of the Brown Alpert Medical School and Miriam Hospital in Providence, Rhode Island.

The findings also shed light on how much exercise may be necessary, he told Reuters Health.

The study defined “active” as getting at least 200 minutes of exercise per week. Patients who, based on survey responses, started getting that much exercise after surgery lost an average of 15 pounds more than their counterparts who remained less active.

For the most part, patients walked for exercise, Bond said, noting that walking is considered the “safest and most practical” way to get active after gastric bypass.

He suggested that patients talk to their doctors about starting an exercise regimen after weight-loss surgery. Getting active, Bond noted, may not only aid in cutting pounds, but may also help manage the medical conditions so often seen in severely obese adults - including diabetes, high blood pressure and High cholesterol.

SOURCE: Obesity 2008.