Poor sleep and low levels of physical activity exacerbate the impact of genetic risk factors for obesity, according to a new study presented at the American Society of Human Genetics (ASHG) 2017 Annual Meeting. The new findings confirm and strengthen previous studies based on self-reported activity.
Researchers at the University of Exeter Medical School in the U.K. have been investigating the genetics of body mass index (BMI) and type II diabetes. In the past, it has been difficult to measure interactions between genetic risk factors and aspects of environment and lifestyle in a systematic way, say the researchers.
“Until recently, physical activity and sleep patterns could not be measured with as much precision as genetic variants, and we relied on diaries or self-report, which can be very subjective,” said Timothy Frayling, Ph.D..
The new study, however, made use of wrist accelerometer data, which is more objective and quantifiable, and a large genetic database of about 85,000 U.K. Biobank participants aged 40 to 70.
“We wanted to find out if obesity-related genes and activity level have an interactive effect on obesity risk — if there is a ‘double whammy’ effect of being both at genetic risk and physically inactive, beyond the additive effect of these factors,” said Dr. Andrew Wood, Ph.D., a postdoctoral researcher.
The researchers calculated a genetic risk score for each participant based on 76 common variants known to be associated with elevated risk of obesity. Then they analyzed this score in the context of accelerometer data and participants’ BMIs.
The research team found the strongest evidence to date of a modest gene-activity interaction. For example, for a person of average height with 10 genetic variants associated with obesity, that genetic risk accounted for a 7.9 pound (3.6 kilograms) increase in weight among those who were less physically active but just 6.1 pounds (2.8 kilograms) among those who were more active.
The findings were similar in analyses of sleep patterns: Among participants with some genetic risk of obesity, those who woke up frequently or slept more restlessly had higher BMIs than those who slept more efficiently.
As of now, the researchers are looking into whether this interaction between genetics and physical activity differs between men and women. They are also studying the effects of activity patterns; for example, whether a consistent level of moderate activity yields different results than low activity levels punctuated by periods of vigorous activity.
“We hope these findings will inform clinicians who help people lose or maintain their weight, and contribute to the understanding that obesity is complex and its prevention may look different for different people,” said Frayling. “Ultimately, with further research, we may have the scope to personalize obesity interventions.”