Older health professionals who adhered to a healthy eating pattern were less likely to gain weight over a 20-year follow-up than their peers.

In fact, adhering to a healthy diet was most beneficial in individuals who had a high genetic risk for obesity in a new study.

These data "for the first time indicate that improving adherence to healthy dietary patterns might diminish the genetic association with weight gain," Tiange Wang, MD, PhD, at Tulane University, New Orleans, Louisiana, and colleagues report in their article published online January 10 in BMJ.

Researchers calculated genetic predisposition for obesity based on the presence of 77 genetic variants associated with body mass index (BMI) in two cohorts of male and female health professionals, and they assessed how closely participants adhered to three healthy eating patterns.

The findings reinforce that a healthy diet is important for everyone, especially people at greatest risk of obesity, Louisa J Ells, a reader in public health and obesity at Teesside University, Middlesbrough, United Kingdom, and colleagues note in an accompanying editorial.

The study shows that "genetic predisposition is no barrier to successful weight management and no excuse for weak health and policy responses," they stress.

"Governments and populations must act to ensure universal healthy diets within health promoting food environments and food systems," they continue.

"This must become the new normal. Only then will we begin to curb and ultimately reverse the global epidemic of obesity."

Genes, Diet, and Long-Term Weight Gain

Previous research has shown that consumption of sugar sweetened beverages and fried foods can magnify the effect of genes on weight gain.

Dr Wang and colleagues aimed to determine how a healthy eating pattern might affect long-term weight gain depending on genetic risk scores for predisposition to obesity.

They identified 8828 women in the Nurses Health Study and 5218 men in the Health Professionals Follow-up Study who were of European ancestry and had complete data, including genetic analysis from blood samples.

At baseline in 1986, women had a mean age of 54, a mean BMI of 26 kg/m2, and a mean weight of 68 kg, and men had a mean age of 55, a mean BMI of 26 kg/m2, and a mean weight of 82 kg.

Researchers calculated a genetic risk score for participants' predisposition to obesity based on the presence of 77 single nucleotide polymorphisms associated with BMI.

Every 4 years the participants replied to a 131-item food frequency questionnaire and researchers determined their BMI.

Diet quality scores were also calculated based on three measures: the Alternate Healthy Eating Index 2010 (AHEI-2010), the Dietary Approach to Stop Hypertension (DASH), and the Alternate Mediterranean Diet (AMED).

The AHEI-2010 score was based on intake of 11 foods and beverages linked with chronic disease, with points for a higher intake of vegetables (excluding potatoes), fruits, whole grains, nuts and legumes, long-chain (n-3) fats, and polyunsaturated fatty acids; a moderate intake of alcohol; and a lower intake of sugar sweetened beverages, red and processed meats, trans fat, and sodium.

The DASH score was based on intake of eight of these foods and beverages.

The AMED score was based on nine components of a Mediterranean diet with points for average or better intake of healthy foods and for average or lower intake of less healthy foods.

Weight Gain Associated With Genes Can Be Counteracted by Good Diet

In general, having an increased genetic risk score was associated with increases in BMI and body weight every 4 years, but this was not the case for the individuals who adhered to a healthy AHEI-2010 or DASH dietary pattern.

Adherence to these healthy diets led to the least increases in BMI in people with a high genetic risk score for obesity.

"Our results suggest that weight gain associated with genetic predisposition can be at least partly counteracted by improving adherence to healthy dietary patterns," Dr Wang and colleagues conclude.

"Importantly, for people who are genetically predisposed to obesity, improving adherence to a healthy diet is more likely to lead to greater weight loss."

These results agree with a previous meta-analysis which showed that people who carry the homozygous FTO allele that predisposes them to obesity may lose more weight than noncarriers through diet and lifestyle interventions.

"It is important to acknowledge the challenges of achieving [a healthy diet] in an obesity promoting environment in which unhealthy food options are cheap, readily available in large portions, and heavily marketed," according to the editorialists.

The study findings "reinforce the critical urgency of comprehensive policies that prioritize healthy food environments and systems, with an emphasis on vulnerable populations."

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BMJ 2018;360:j5644. Article

BMJ 2018;360:k7 Editorial