Obesity surgery may curb 'drive to eat'

NEW YORK (Reuters Health) - Gastric bypass surgery may reduce the high drive to eat that is typically found in severely obese people, 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 and absorb in the digestive tract, can spur substantial weight loss and help control obesity-related conditions like diabetes.

Studies have also suggested that the obesity surgery may alter secretion of hunger-regulating hormones -- enhancing levels of appetite-dampening hormones and curbing hunger-stimulating ones.

The new study, reported in the American Journal of Clinical Nutrition, looked at whether gastric bypass might also curb so-called "hedonic" hunger. This refers to eating spurred not by actual physical hunger, but by the desire to eat because it brings pleasure, or simply because a person wants food.

It's thought that this "drive to eat" even in the absence of hunger is a contributor to obesity, and one reason why many obese people find it so hard to maintain weight loss over the long haul.

"Our study shows that the drive to eat is reduced after gastric bypass surgery," lead researcher Dr. Bernd Schultes told Reuters Health in an email. "That means the surgery has an impact on thoughts and feelings about food and eating. This is more than just reducing hunger."

The findings imply that gastric bypass may help "correct" a dysregulation in hedonic hunger that affects severely obese people, explained Schultes, who heads the Interdisciplinary Obesity Center at Kantonsspital St. Gallen in Rorschach, Switzerland.

The findings are based on questionnaire responses from 136 adults who had undergone gastric bypass at least one year earlier, 123 severely obese individuals who were being considered for the surgery, and 110 normal-weight to mildly overweight adults.

The questionnaire gauged participants' motivation to eat highly palatable foods, but not their actual consumption. It asked, for example, the extent to which the respondent agreed with statements like, "I find myself thinking about food even when I'm not physically hungry," and "When I eat delicious food I focus a lot on how good it tastes."

Overall, Schultes' team found, severely obese participants scored "markedly higher" on this drive-to-eat scale than the other two groups. The gastric-bypass group, meanwhile, did not differ from the non-obese group.

Obese participants did not, however, appear to take greater pleasure from food. Instead, their questionnaire responses indicated that they "wanted" food more than the other two groups did, according to Schultes and his colleagues.

If gastric bypass does in fact dampen this want for food, it is not clear how it would do so. One possibility, according to the researchers, is that it affects certain appetite-regulating brain structures by altering the secretion of hunger-related hormones in the gut.

Future studies, according to Schultes, should follow a group of gastric-bypass patients over time -- seeing whether their hedonic hunger declines after surgery, how long the change lasts, and whether an individual's shift in hedonic hunger affects his or her long-term weight loss.

Research should also look at the relationship between patients' post-surgery changes in gastrointestinal hormones and their shifts in hedonic hunger, Schultes noted.

"If we understand the mechanisms by which gastric bypass surgery reduces the hedonic drive to eat," he said, "we can potentially mimic these effects (with) other non-surgical interventions."

SOURCE: link.reuters.com/rer36m American Journal of Clinical Nutrition, online June 2, 2010.