The Success Of Gastric Bypass Surgery May Be Affected By Genetic Factors

A new study published in The American Journal of Human Genetics has discovered that amount of weight a person who has had gastric bypass surgery will lose can be determined in part by a DNA sequence variation. The identification of these markers can predict postoperative weight loss as well as provide insight into physiological mechanisms. This gene variant found on chromosome 15 can explain the variations in the success of the surgery and can help doctors determine who will benefit most from the procedure. That genetics appears to play such a significant role in the success of gastric bypass surgery in individuals adds to the evidence that obesity is a result from dysfunction of biological mechanisms that regulate fat mass and body weight; and that obesity is not just a result of aberrant behavior or limited willpower.

This is the first study that has identified genetic predictors of weight loss following gastric bypass, according to researchers. Due to this research, it is now known that bypass surgery works not just by physically restricting food intake but also through physiological effects, such as regulating appetite so that hunger is decreased, enhancing satiating, and increasing a person’s daily energy expenditure. New treatment options for obesity and related causes, including diabetes and cardiovascular disease, could start being developed because of this new information.

This study conducted a genome-wide association study on over 1,000 patients who had undergone gastric bypass surgery at a Boston medical facility from 2000 to 2011. Nearly two million gene sites were analyzed for associations between specific variants and the percentage of weight that was lost following the surgery. The variant on chromosome 15 was closely associated with weight loss. If an individual had two copies of the beneficial version of the gene, there was an average weight loss of nearly 40 percent of pre-surgery weight (if there was just one copy the weight loss was approximately 33 percent). A person who completely lacked the beneficial variant lost less than 30 percent of their pre-surgical weight.

A pair of predictive models were developed by the researchers. One combined the chromosome 15 gene variant with clinical factors such as age, gender, and exercise behaviors. The other model included 12 other DNA variations that were studied to determine their usefulness in weight loss treatment planning.

The study found that none of the predictive gene sites that were identified in this study had been previously established as influencing obesity. Therefore the researchers believe that there is a different set of genes responsible for the benefits of gastric bypass. They also believe that drugs could be developed that would target activity in those genetic regions, leading to the same benefits as gastric bypass without needing surgery.

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