Obesity is a highly heritable condition with considerable penetrance, especially in our obesogenic enviroment.
However, as I have pointed out before, having a genetic predisposition for obesity (like having a genetic predisposition for other diseases such as diabetes or high blood pressure) does not mean your fate is chiseled in stone. Lifestyle changes can significantly reduce the risk, but those with a stronger genetic predisposition will have to work a lot harder at not gaining weight than those who are naturally slender.
That said, a new study by Liu and colleagues from Harvard University, published in Social Science & Medicine, shows that better education may offset a substantial proportion of the genetic risk for obesity and/or diabetes.
The researchers created genetic risk scores for obesity and diabetes based on single nucleotide polymorphism (SNPs) confirmed as genome-wide significant predictors for BMI (29 SNPs) and diabetes risk (39 SNPs) in over 8000 participants in the Health and Retirement Study.
Linear regression models with years of schooling indicate that the effect of genetic risk on both HbA1c and BMI was smaller among people with more years of schooling and larger among those with less than a high school (HS) degree compared to HS degree-holders.
As one may expect, estimates from the quantile regression models consistently indicated stronger associations for years of schooling and genetic risk scores at the higher end of the outcome distribution, where individuals are at actual risk for diabetes and obesity.
In other words, the greater the genetic risk for diabetes or obesity, the greater the positive impact of finishing high-school or college.
In contrast, having less than a high-school education augmented the genetic risk for these conditions.
From these findings the authors conclude that,
“Our findings provide some support for the social trigger model, which speculates that the social environment can attenuate or exacerbate inherent genetic risks. Furthermore, it suggests social stratification may shape how genetic vulnerability is expressed. Social hierarchies based on socioeconomic status determine the health status of individuals. According to fundamental cause theory, policies and interventions must address social factors directly to have a population-level impact on disease risk . Our results show how education, a fundamental cause of health and disease, can serve as a valuable resource that offsets even innate biological risk. Education increases an individual’s ability to adapt, modify, and use surrounding resources. As such, polices that reduce disparities in education may help offset underlying genetic risk.”
This study strongly supports my view that one cannot (and should not) ignore genetic risk when studying the effect of environmental or behavioural factors in populations or individuals. Indeed, the greatest benefit of these interventions clearly appear to be found in those with the highest genetic risk.
Liu SY, Walter S, Marden J, Rehkopf DH, Kubzansky LD, Nguyen T, & Glymour MM (2014). Genetic vulnerability to diabetes and obesity: Does education offset the risk? Social science & medicine (1982) PMID: 25245452