Epidemiology
and Prevention/Nutrition, Physical Activity and Metabolism 2012
Women who walked briskly for at least 1 hour per day attenuated their
genetic predisposition to obesity, according to results of a study presented at
the American Heart Association’s Epidemiology and Prevention/Nutrition,
Physical Activity and Metabolism 2012 Scientific Sessions.
In contrast, those who followed a sedentary lifestyle that included
prolonged TV watching accentuated their genetic disposition to
obesity and increased BMI, researchers found.
The study included longitudinal data from 7,740 women who participated
in the Nurses’ Health Study and 4,564 men from the Health Professionals
Follow-up Study. Researchers collected data on physical activity and TV habits
2 years before assessment of BMI. Genetic predisposition score was calculated
on the basis of 32 established BMI-predisposing variants. The effect of genes
on obesity was measured by differences in BMI per point of the
genetic predisposition score, corresponding to each
BMI-increasing gene, according to a press release.
Each BMI-increasing gene was associated with a 0.13 kg/m2
increase in BMI. This effect was reduced in those with the highest level of
physical activity compared with those with the lowest (0.08 kg/m2
vs. 0.15 kg/m2; P<.001). The genetic effect on BMI was
more pronounced in those who spent more than 40 hours per week watching TV
compared with those who watched 1 or fewer hours per week (0.34
kg/m2 vs. 0.08 kg/m2; P=.001).
One hour of brisk walking per day was associated with a 0.06
kg/m2 reduction in the genetic effect on BMI. Each 2-hour per day
increment in TV watching was associated with a 0.03 kg/m2 increase
in genetic effect on BMI, according to the results.
For this study, obesity was defined as a BMI of at least 30.
“Our data suggest that both increasing exercise levels and reducing
sedentary behaviors, especially TV watching, independently may mitigate the
genetic predisposition to increased BMI,” Qibin Qi, PhD,
postdoctoral research fellow in the department of nutrition at Harvard School
of Public Health, and colleagues concluded.
How the function of these genes affect BMI is not clear, according to
Qi.
“These genes were just identified in the past 5 years and the exact
functions of the genetic variants are still unknown,” he said in a press
release. “Future studies will be needed to uncover the underlying
mechanisms.”
For more information:
Disclosure: Dr. Qi reports no relevant financial disclosures.
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Richard A. Stein
Courtesy of the American Heart Association
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It is reasonable to assume that people who are going to be more
physically active are going to be less obese. Certainly, we are learning a lot
more about the negative impacts of sedentary behavior, and are using TV time as
a reasonable correlate of sedentary behavior. The take-home message is that
there are genes that predict propensity for obesity, but, in the case of
obesity, genes are not destiny. Essentially, physical activity behavior can
play an important role in the majority of patients to help them stay at an
ideal body weight despite having gene profiles that are predisposed to become
obese. It emphasizes the very importance of physical activity lifestyle and
avoiding obesity.
– Richard A. Stein, MD
Professor of
Medciine
New York University
Disclosure: Dr. Stein reports no relevant financial
disclosures.