Monday, March 30, 2009
Photo by MASH DnArt
Several studies in recent years have suggested that people with specific genetic profiles are at increased risk of obesity. The FTO gene in particular has received a lot of press since a 2007 article in Science reported that individuals who are homozygous for the risky FTO allele are an average of 3 kilograms (roughly 6.6 lbs) heavier than individuals who do not have the risky allele. After reading one of the mainstream news article on the topic (such as this 2007 article from the BBC), you could be excused for thinking that obesity is nearly completely genetically determined. Luckily, this is not the case - your genes are just one of many factors which influence your risk of numerous diseases, obesity included. This point was nicely illustrated by an article that was published by researchers at Brown Medical School in the April 1 issue of the American Journal of Clinical Nutrition.
In their recent study, Jeanne McCaffery and colleagues examined obesity rates in 8627 adult male twins. As we might expect, obesity exhibited a strong hereditary component (e.g. individuals with obese parents were more likely to be obese themselves). However, they found that the heritability of obesity was significantly reduced in individuals who performed vigorous physical activity. In other words, individuals who performed vigorous physical activity were less likely to be obese, regardless of their genetic makeup. As with the findings of similar studies, the results of this study suggest that genes are strong predictors of obesity in sedentary individuals, but that this relationship is significantly weakened in individuals who are physically active. Interestingly, in this study the positive influence of vigorous activity appeared to increase with age, such that obesity was even less genetically determined in vigorous older men than in vigorous younger men. Unfortunately the effects of diet and low-to- moderate intensity physical activity were not examined in this study, although I hope I am not alone in assuming that they are likely to play a role as well.
Hopefully the results from this study are not all that surprising to regular readers of this blog. Genes affect our risk for numerous diseases (cancer and high blood pressure jump to mind), but rarely are they completely deterministic. In fact, I would wager that most of us are at heightened risk for some disease or another (what a wonderful thought to start your week...). It is also not surprising that some individuals show a greater propensity for the storage of body fat - an adaptation which would have been quite advantageous until relatively recently. The important thing to remember is that by living a healthy lifestyle (or healthstyle as Darya Pino would call it), you lower your risk of obesity, regardless of your genetic background. As the saying goes, "genes load the gun, but the environment pulls the trigger".
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