Weight loss bypass surgery may muffle temptation
16 October, 2012
ISLAMABAD: People who've had gastric bypass surgery might make healthier eating choices than those who opt for the weight loss procedure known as gastric banding, say UK researchers who found bypass patients less tempted by sweets and other fattening foods.
After surveying patients who had either type of surgery, and performing brain scans on several dozen of them, Dr. Tony Goldstone of Imperial College London and Hammersmith Hospital and his colleagues found that even deep down in their brains, the gastric bypass patients seemed to like high-calorie foods less.
"The results suggest that gastric-banding patients had to exert quite a lot of self-control over their eating behavior. Banding patients also had higher concern about their weight," Goldstone told Reuters Health.
In contrast, gastric bypass patients "don't feel they have to exert as much cognitive control over what they're eating," said Goldstone, who presented the findings October 4th at the Obesity Society's annual meeting in Orlando, Florida.
The two weight loss operations have similar broad goals -- to shrink the stomach so people feel full with less food. In gastric bypass, the stomach is surgically reduced and one end of it is rerouted to bypass part of the small intestine. With gastric banding, a silicone band placed around the top of the stomach reduces its capacity.
Although gastric banding is more popular, in part because the band can be removed, previous research has found gastric bypass patients seem to lose more weight and lose it faster than banding patients. The reasons for the differences are still unclear.
Goldstone's team studied 30 gastric bypass patients, 28 gastric banding patients and 20 people who did not have weight loss surgery. All the participants started out obese and the two surgery groups had lost similar amounts of body weight since their respective procedures, an average of 28 percent.
Since banding patients lose weight more slowly, those in this study had undergone their procedure an average of 18 months earlier, compared to the bypass patients at 10 months post-surgery.
Participants filled out an eating behavior questionnaire, and 20 people in each group underwent functional magnetic resonance imaging (fMRI) while looking at pictures of food.
Among the significant differences in questionnaire responses, researchers found, the gastric bypass patients reported having to restrain themselves less, or finding it easier to restrain themselves from eating poorly. They also did less impulsive eating -- eating something on sight, not out of hunger -- and less eating to boost their mood, or "emotional eating."
Those who underwent fMRI had fasted overnight, and then viewed pictures of foods and ate ice cream during the brain scan. The gastric bypass patients rated the ice cream and pictures of high-calorie foods as less appealing than did the gastric banding patients.
Bypass patients also showed lower activity in brain areas like the orbitofrontal cortex (associated with a reward response), the amygdala (associated with emotion) and in the ventral striatum (which would register the expectation of a reward like food).
Goldstone theorizes that gut hormones that trigger a feeling of fullness after eating are released more quickly in gastric bypass patients, and these chemical signals may be influencing those patients' long- and short-term responses to food in a way the gastric banding patients don't experience.
"The connections between the biology of obesity and the mechanisms of the surgery we use is really a new science established in the last three to five years," said Dr. Robin Blackstone, president of the American Society for Metabolic and Bariatric Surgery, who was not involved in the study. "Now that we understand more about how these procedures are working, it makes sense that the bypass patients would have more control. The band would not produce those same effects."
"Bypass results in more weight loss than the band and it is a more sustainable weight loss," Blackstone added. "Now we begin to understand why that is, because it has these kinds of effects."
It's not possible yet to say that one type of surgery or another is better for a certain type of patient, noted Blackstone, who is also the medical director at Scottsdale Healthcare Bariatric Center in Arizona.
"A lot of people are working to figure out which procedure is best for which patients," she said.
"People that are motivated to use the band generally don't have much weight to lose, or they're attracted by the safety profile -- the lower mortality rates -- and that it's reversible," Blackstone said.
"The more we begin to understand about patients individually, including the genetic components of their obesity, we'll be able to match a procedure really well for them. We just don't know how to select people out for each procedure," she said.
Goldstone said his next step will be determining whether the reduced response to fattening foods seen in gastric bypass patients actually translates into their making healthier , low-calorie food choices.