People with a high genetic risk for obesity lost more weight than those with low genetic risk when they stuck to a long-term healthy diet, according to a 20-year prospective cohort study.
For every standard deviation increase in diet quality score based on the Alternative Healthy Eating Index-2010 diet, BMI decreased by 0.18, corresponding to 0.50 kg (about 1.1 lbs) weight loss, in individuals at high genetic risk for obesity. For those at low risk, BMI decreased by only 0.12, corresponding to 0.35 kg weight loss (P=0.001 for the interaction), said Lu Qi, MD, PhD, of Tulane University in New Orleans, and colleagues.
For each increase in diet quality score based on the Dietary Approach to Stop Hypertension (DASH) diet, BMI dropped by 0.19 for individuals at high genetic risk for obesity, but only 0.14 for those at low risk (P=0.001), they reported in BMJ.
“Our results suggest that weight gain associated with genetic predisposition can be at least partly counteracted by improving adherence to healthy dietary patterns. Importantly, for people who are genetically predisposed to obesity, improving adherence to a healthy diet is more likely to lead to greater weight loss,” the authors said.
Although the observed genetic effects were modest in magnitude, their-long term effects could be “substantial” because they accumulate over a person’s lifetime, they explained. “Furthermore, long term, dramatic weight loss is difficult to achieve, even in the context of weight loss interventions. Therefore, even modest weight loss or simply maintaining weight from adulthood onward, compared with gaining weight, may have a substantial effect on population health,” they said.
The findings “help to dispel misconceptions that a genetic predisposition will inhibit successful weight management,” said Louisa Ells, PhD, of Teesside University in Middlesbrough, England, and colleagues, in an accompanying editorial. “The findings provide encouraging new evidence that although a better diet can improve weight loss, the effect may be greatest in those with the highest genetic predisposition for obesity.”
In addition, the study “underlines the critical importance of achieving healthy diets for everyone. This is still a challenge for many, however, with poor diet being a leading risk factor for death and disability globally. Genetic predisposition is no barrier to successful weight management and no excuse for weak health and policy responses,” Ells’ group wrote.
Qi’s group prospectively analyzed data on 8,820 women in the Nurse’s Health Study and 5,218 men in the Health Professionals Follow-Up Study. All participants had genotype data available based on genome-wide association studies and were free of diabetes, cancer, and cardiovascular disease at baseline.
Participants were categorized as having high, intermediate, or low genetic risk for obesity based on an analysis of 77 single nucleotide polymorphisms known to be associated with BMI and body weight.
Height was measured at baseline, and information on diet and changes in body weight were gathered every 4 years with questionnaires, from 1986 to 2006. The authors used multivariate generalized linear statistical models to look for associations between genetic predisposition to obesity, adherence to a healthy diet, and weight loss over time.
The biological mechanisms underlying the findings were not clear. Several genes associated with BMI are known to be involved in central appetite regulation and energy homeostasis, and they may also be responsible for the interactions observed in the study, the authors said. “However, we cannot exclude the involvement of other biological pathways, and future functional studies are needed to provide biological insights into the gene by diet interactions on weight change,” they added.
An important limitation of the study was that it included only health professionals of European descent living in the U.S., so the results may not apply to other demographic or racial/ethnic groups, Qi’s group noted.
“Our findings highlight the importance of improving adherence to a healthy diet in the prevention of weight gain, particularly in people genetically predisposed to obesity,” they concluded.
The study was funded by the NIH
Qi and co-authors, as well as Ells and co-authors, disclosed no relevant relationships with industry.
Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner