Excess Weight Loss after Bariatric Surgery: The Influence of Catechol-O-Methyltransferase (COMT) Polymorphism (Val108/158Met), Sociodemographic Variables and Physical Activity

Abstract

Background: In the treatment of morbid obesity bariatric surgery has become the method of choice. Dopamine is the primary modulator of the brain’s reward system and plays an essential role in the regulation of food intake. The role of dopamine is well documented in weight regulation and food intake in both animal models and humans. Still, the role of dopamine has not been well studied for weight loss. Catechol-O-methyltransferase (COMT) degrades catecholamines and estrogens are both known to be important risk factors for cardiovascular diseases and consequently obesity. The gene coding for COMT contains a Val108/158Met polymorphism that exerts a considerable influence on enzymatic activity. We hypothesized that this polymorphism might influence weight loss in obese patients, who previously underwent gastric banding surgery. In obesity research, it is known that women tend to lose more weight than men, and weight before surgery might also affect the outcome of weight loss efforts. Several studies have shown that physical activity (PA) plays an important role in maintaining weight as well as in both non-surgical and surgical weight loss. Therefore, we examined whether gender, age, weight before surgery and PA are good predictor variables for the outcome of surgical weight loss. Methods: One to six years after bariatric surgery 74 adults underwent a semi-structured interview. In a second step data on the post-surgical PA level were collected with the Moorehead-Ardelt Quality of Life Questionnaire. Finally, mouth swabs were used for genotyping. Results: 54 women and 20 men were enrolled between January 2004 and September 2009. Short-term EWL in the mid-activity genotype dopamine group (GA) was significantly higher (p = 0.007) than was short-term EWL in the low-activity genotype dopamine group (AA) or in the high-activity genotype dopamine group (GG). However, there were no significant differences between the COMT groups with respect to long-term EWL. Long-term we determined that EWL is significantly positively influenced by PA and negatively by gender. The effect of EWL was more pronounced in female than in male subjects. Conclusion: Various individual genotypes of the COMT polymorphism (Val108/158Met) make an impact only on short-term EWL, but not on long-term EWL. However, gender and PA proved to be good surgical weight loss predictors for long-term EWL.