Variations of a particular gene, known as the fat mass and obesity associated (FTO) gene, are widely acknowledged to be linked with a high body mass index, according to background material in the study, which is published in the Archives of Internal Medicine.
Evadnie Rampersaud, MSPH, PhD, then of the University of Maryland School of Medicine and now of the University of Miami, and colleagues examined how lifestyle affected the weight of people with a genetic predisposition to being overweight.
Researchers studied DNA samples of 704 healthy Amish adults, collected between 2003 and 2007. Participants also underwent physiological tests, including a seven-day measurement of physical activity using an accelerometer, which participants wore on their body. The instrument measured activity level at 15-second intervals.
The participants had an average age of 44 years; 53% were men. Fifty-four percent of the men were overweight and 10% were obese. About 64% of the women were overweight and 31% were obese.
The group was divided into people with high activity levels and low activity levels. The highly active group burned about 900 more calories per day than the lower activity group. That equals about three to four hours of moderately intensive physical activity, such as brisk walking, house cleaning, or gardening, according to the researchers.
The study showed, as past research has, that people with certain variations of the FTO gene were more likely to be overweight. However, the researchers found that being genetically predisposed to obesity "had no effect on those with above average physical activity scores."
As obesity increasingly becomes a global health concern, understanding all aspects of the FTO gene is important, the researchers say. Variants of the FTO gene are prevalent -- about 30% of European populations have such variants, according to the study. The gene variants are associated with a greater than 20% risk for obesity, write the researchers.
Study authors conclude, "These findings emphasize the important role of physical activity in public health efforts to combat obesity, particularly in genetically susceptible individuals."