People who adopt a healthy diet to lose weight may get better results when they have a greater genetic risk for obesity, a US study suggests. "People with high genetic risk have an elevated risk of developing obesity; however, our data indicate that genes are not destiny," said senior study author Lu Qi of the School of Public Health and Tropical Medicine at Tulane University in New Orleans.
"Healthy dietary habits would prevent weight gain, and such effects are more evident in those with high genetic risk," Qi said by email. Researchers scored study participants' diets, awarding more points for higher intake of foods associated with a lower risk of chronic disease, such as fruits, vegetables, whole grains, nuts, and legumes as well as lower intake of unhealthy foods like processed meats and sweets.
Then, to assess participants' genetic risk for obesity, the study team focused on 77 small variations in DNA that are associated with obesity in people of European descent. People get one gene copy from each parent, and researchers scored genetic risk from 0 to 154 based on the total number of obesity-related versions of genes, known as alleles, that participants could inherit from their parents.
All of the study participants worked in healthcare: 8,828 female nurses and 5,218 male health professionals. Overall, the nurses had an average genetic obesity risk score of 69.5 and the men typically had a risk score of 69.3. On average, each 10-point increase in genetic obesity risk was associated with weight gain of 0.05 kilograms (0.11 pounds) every four years, the study found.
During 20 years of follow-up, however, the connection between weight gain and genetic obesity risk was strongly influenced by diet quality, with people at highest genetic risk seeing the greatest effect on weight from healthy eating habits. Every four years, increases in diet quality were associated with weight loss of 0.35 kilograms (0.77 pounds) in people with the lowest genetic risk of obesity and weight loss of 0.5 kilograms (1.1 pounds) in participants with the highest genetic obesity risk, researchers report in the BMJ.
The study wasn't a controlled experiment designed to prove whether or how certain dietary habits might influence weight gain for people with different genetic risk for obesity, the authors note. Another limitation of the study is that researchers relied on study participants to accurately recall and report their food and drink intake, which might not always offer a reliable picture of eating habits. In addition, the results from predominantly white participants might not reflect what would happen with other racial or ethnic groups.
Even so, it's possible that certain foods might alter the activity of genes related to obesity, said Dr Ramon Estruch of the Instituto de Salud Carlos III in Madrid, Spain. People at high risk for obesity might, for example, lose more weight or avoid gaining weight if they eat diets rich in fruits, vegetables, fish and other foods with lots of omega-3 fatty acids, and whole grains, Estruch said by email. Similarly, they might have a healthier weight if they avoided things like sodas and fried foods.
"These recommendations work in all subjects, but especially in those with a genetic predisposition to become overweight or obese," Estruch added.
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