by naveen chowdary
The study investigated whether variations of a particular gene, known as the fat mass and obesity associated (FTO) gene, are linked with a high body mass index (BMI) in Old Order Amish individuals.
It also examined whether the detrimental associations of FTO gene variants can be lessened by an increase in physical activity. The University of Maryland study was published in the August issue of the Archives of Internal Medicine.
Seven hundred and four healthy adults with valid genotype data were selected from a sample group who had participated in the Heredity and Phenotype Intervention (HAPI) Heart Study, an investigation of gene vs. environmental interactions in cardiovascular disease.
Participants were members of the Older Amish community of Lancaster County, PA. Because of simi larities in tradition, formal education, and geographic location, the Old Order Amish have a relatively homogeneous lifestyle, including dietary habits.
Most men are farmers or work in physically demanding occupations. Women are homemakers and usually take care of many children. The mean age of the participants was 43.6 years. The study included slightly more men than women (53% male vs. 47% female).
Subjects who were defined as overweight had a BMI ≥25, and those who were considered obese had a BMI ≥30. The mean BMI was higher in women than in men. Additional measures of other obesity-related traits were obtained, including waist circumference and body composition (fat mass, lean mass, and derived percentage of body fat). The prevalence of overweight and obesity in the Amish men was 54.0% and 10.1%, respectively; in women, it was 63.7% and 30.5%, respectively.
Physical activity measurements were taken for each participant for seven consecutive 24-hour days. Based on these findings, researchers were able to compare the genotype associations of FTO variants in the Amish subjects in terms of “high” and “low” physical activity levels.
For women, mean energy expenditures were 2610 kilocalories per day for the low-activity group and 3590 kcal/day for the high group. For men, average energy expenditure for the low-activity group was 3130 kcal/day, compared with 3990 kcal/day for the high group.
Re searchers reported that activity levels in the high-activity stratum were approximately 900 kcal higher than in the low-activity one. High-level activities consisted of three to four hours of moderately intense physical activity, such as brisk walking, housecleaning, or gardening.
A DNA sequence variation—in the form of single-nucleotide polymorphisms (SNPs)—asso ci a ted with BMI and related measures were seen only among the less physically active subjects.
By contrast, in the more physically active group, the FTO variant associations were much smaller and not statistically significant. Because the FTO geno type was not associated with physical activity, this finding suggests a strong moderating effect of physical activity on the deleterious effects of FTO variants, according to the researchers.
The study also reported that participants with certain variations of the FTO gene were more likely to be overweight. But the function of the FTO gene is still not completely understood, and its variants are prevalent, according to lead author Evadnie Rampersaud, MSPH, PhD.
In fact, about 30% of European populations have such variants, which are associated with a greater than 20% risk for obesity, she said.
“Weight increase resulting from the presence of these SNPs is much smaller and not statistically significant in subjects who are very physically active,” said Ram per saud. “This finding offers some clues to the mechanism by which FTO influences chan ges in BMI and may have im portant implications in targeting per son alized life style recommendations to prevent obesity in genetically susceptible individuals.”
More research is needed to determine the amount of activity required to negate the effect of an FTO-related genetic predisposition to weight gain, according to Rampersaud.
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