Exercise Reduces Genetic Risk of Obesity?

In the never-ending nature-nurture debate (which is not really a sensible debate at all), the nurture side may have scored a minor “win” this week.

In a paper just released online in PLoS, Li and colleagues from Cambridge University, UK, use the EPIC study to demonstrate that being physically active may protect from the obesogenic impact of obesity promoting genes.

The researchers examined 12 genetic markers (SNPs), previously shown to increase the risk for obesity, in a population-based sample of 20,430 individuals (aged 39-79 y) from the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort with an average follow-up period of 3.6 y.

Mathematical models were used to examine interactions between a genetic predisposition score (based on counting the number of obesity promoting alleles) and its interaction with physical activity on BMI/obesity risk and BMI change over time.

While each additional BMI-increasing allele was associated with 0.154 increase in BMI (equivalent to 445 g in body weight for a person 1.70 m tall), this association was more pronounce in inactive people (592 g in weight) than in active people (379 g in weight).

Similarly, each additional BMI-increasing allele increased the risk of obesity 1.116-fold in the whole population, but significantly more in inactive individuals (1.158) than in active individuals (1.095).

Physical activity also modified the association between the genetic predisposition score and change in BMI during the follow-up period.

The authors conclude that living a physically active lifestyle is associated with a 40% reduction in the genetic predisposition to common obesity, as estimated by the number of risk alleles carried for any of the 12 genetic markers.

The study makes two important points:

1) Yes, there are genetic variants that can make it easier for some people to gain weight.

2) Some of that genetic predisposition can be reduced with physical activity.

Obviously, the higher the genetic risk, the greater the physical activity that may be required to prevent weight gain – whether this is practical or feasible for everyone is a very different matter.

Seems that the old saying, “The genes load the gun, the environment pulls the trigger”, still holds true.

Edmonton, Alberta

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Li S, Zhao JH, Luan J, Ekelund U, Luben RN, Khaw KT, Wareham NJ, & Loos RJ (2010). Physical Activity Attenuates the Genetic Predisposition to Obesity in 20,000 Men and Women from EPIC-Norfolk Prospective Population Study. PLoS medicine, 7 (8) PMID: 20824172