Certain genetic markers may explain why some people who drink similar amounts of soda or other sugar-sweetened beverages are more likely to be obese than others.
Participants in a new study who had more of these markers were at a greater risk of obesity than those with fewer markers — and the more sugar-sweetened beverages that people drank, the wider the gap grew between the groups, in terms of obesity risk.
These markers are not new to science — people who have them are thought to be genetically prone to obesity.
But little was known about how lifestyle factors, such as the type of food and beverages that people consume, influence weight gain for people with these markers.
The new study suggests people with a genetic predisposition to obesity are more susceptible than others to the harmful effects of sugar-sweetened beverages, the researchers said.
"Our data suggest genetic factors and environmental factors may work together in affecting obesity risk. For those who carry high genetic risk, their risk of obesity could be lessened by [making] healthier beverage choices," said study researcher Lu Qi, assistant professor at Harvard School of Public Health.
Qi and colleagues analyzed information from more than 33,000 adults who participated in three studies that began in the 1980s and 1990s. Every four years, participants answered questions about their food and beverage intake.
Participants also had their genomes analyzed for the presence of any of 32 genetic markers linked to obesity. They were given a score — based on the number and type of genetic markers they had — that reflected their genetic predisposition to obesity.
Not surprisingly, those with a higher genetic predisposition to obesity were more likely to be obese.
But the link between genetics and obesity was stronger among those who drank sugar-sweetened beverages.
For every 10-point increase in genetic risk score, the risk of being obese increased about 35 percent for those who drank less than one serving of sugar-sweetened beverages monthly, but increased 59 percent among those who drank one to four servings monthly, and 235 percent among those drinking one or more servings daily.
"Our findings further underscore the need to test interventions that reduce the intake of sugar drinks as a means of reducing the risk of obesity and related diseases," the researchers write in the Sept. 21 issue of the New England Journal of Medicine.
Sugary drinks likely contribute to obesity because they are high in calories but they don't satiate the appetite, and so people often do not cut back on the calories they eat to compensate for those they consume in liquid form.
Further research is needed to determine why these markers increase the risk of obesity specifically when people drink sugar-sweetened beverages, the researchers said.
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