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US research published in the BMJ has shown that the benefits of sticking to a healthy diet to prevent long term weight gain are greater in people at high genetic risk for obesity than in those with lower risk. The researchers analysed data from two large studies of US health professionals – 8828 women in the Nurses’ Health Study and 5218 men from the Health Professionals Follow-up Study from 1986 to 2006. Genetic risk score was calculated on the basis of 77 gene variants known to influence body mass index. Changes in body mass index and weight were calculated every 4 years. Changes in dietary patterns were also assessed every 4 years with three diet quality scores: the Alternate Healthy Eating Index 2010 (AHEI-2010), Dietary Approach to Stop Hypertension (DASH), and Alternate Mediterranean Diet (AMED). These diets are all rich in fruit and vegetables, nuts and whole grains, and low in salt, sugary drinks, alcohol and red and processed meats. After 20 years’ follow-up, the researchers found that improving adherence to the AHEI-2010 and DASH was associated with decreases in body mass index and body weight, and that the effect was more prominent in people at high genetic risk for obesity than those with low genetic risk. In addition, they noted that “the genetic risk of weight gain is attenuated by improving adherence to these healthy dietary patterns”. No clear interaction pattern was found for AMED. The authors pointed out that this was an observational study, so no firm conclusions could be drawn about cause and effect. Nevertheless, they said that their findings “highlight the importance of improving adherence to a healthy diet in the prevention of weight gain, particularly in people genetically predisposed to obesity”.