Studies show that 60 to 80 percent of children born to two obese parents will themselves become obese, compared with 9 percent of children who are born to lean parents. Research on identical twins demonstrates similarly high rates of inheritance. On the other hand, studies comparing the weights of adoptees with the weights of their biological and adopted parents indicate that genetic factors are responsible for only about a third of the difference in weight. While the degree to which heredity affects one’s weight has yet to be determined definitively, it is clear that heredity seems to influence the number of fat cells in the body, how much and where fat is stored, and how much energy the body uses while at rest.
If you’re one of the people at high genetic risk for obesity, your fate isn’t sealed. A 2018 study in the journal BMJ suggests that a healthy diet can help you control your weight even more than it helps those at low genetic risk.
The investigators looked at data on more than 13,000 nurses and other health professionals over two decades. Genetic risk was calculated based on 77 gene variants linked to body weight. Changes in participants’ diets were assessed every four years using three standard healthy-eating indexes (based, for instance, on the anti-hypertension DASH diet), all rich in vegetables, fruits, whole grains, and nuts and low in red or processed meats, added sugars, and salt.
After 20 years, the researchers found that the more participants improved their diets, the more likely they were to lose excess weight or at least not gain weight, and that this association was strongest in the one-third judged to be most genetically predisposed to obesity.