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Are Athletes More Prone to Obesity?

One of the interesting but ‘paradoxical’ observations in my clinical practice is the rather large number of patients presenting with severe obesity, who have histories of successful competitive sports careers.

I have previously written about the notion that perhaps the same genes that can make you a successful athlete may well pose a risk factor for obesity.

Now, a study by Xue and colleagues from the University of Texas, published in PLoS One, suggests that genes that increase metabolic efficiency may indeed explain both the higher athletic prowess as well as the increased risk for obesity in Africans.

It is certainly no secret that Africans have held the most world records for track and field sports, including the men’s and women’s 100-meter dash, 200-meter dash, 400-meter dash, 800-meter dash, and even marathons.

Based on previous observations that Africans tend to expend less energy for the same level of physical activity as Europeans, the researchers reasoned that the genes responsible for this may also contribute to an increased predisposition to weight gain in this population.

The researchers used data from the HapMap project to examine African, Asian and European subjects for 231 common variants with possibly harmful impact on 182 genes involved in energy metabolism

This analysis found that Africans (3 out of 4 groups) had a significantly smaller genetic risk in the of possessing genes that would lead to inefficient energy metabolism than Europeans and Asians

As they point out:

‘In sport competitions, athletes need massive amounts of energy expenditure in a short period of time, so higher efficiency of energy generation might help make African-descendent athletes more powerful. On the other hand, higher efficiency of generating energy might also result in consuming smaller volumes of body mass. As a result, Africans might be more vulnerable to obesity compared to the other races when under the same or similar conditions.”

Obviously, as there is no such thing as the ‘African’ genome, in that all such genetic variants are also found in non-Africans, it may be reasonable to speculate that in general, genes that improve energy-efficiency (or rather absence of genetic variants that reduce it), thus increasing athletic prowess, can contribute to increased risk for obesity (when exercise ceases) in all populations.

While this notion is not dissimilar to the ‘thrifty genotype’ hypothesis, it does provide a novel ‘spin’ in that it suggest that the same ‘thrifty genotype’ that promotes obesity may also be responsible for making you a good athlete.

This certainly sounds very plausible considering how many obese patients I see, who have histories of being successful athletes. It also perhaps explains why so many of my patients can maintain rather high levels of physical activity once they find their way back into sports (for e.g. after bariatric surgery).

Edmonton, Alberta

Xue C, Fu YX, Zhao Y, Gong Y, & Liu X (2011). Smaller genetic risk in catabolic process explains lower energy expenditure, more athletic capability and higher prevalence of obesity in africans. PloS one, 6 (10) PMID: 22016803


  1. Honestly, I think a large part of this — I’d hazard a guess that it would be the larger part — is that athletes are used to EATING like athletes, and don’t stop when they become sedentary. I’d wager that any genomic effect would be swamped by the difficulty of breaking the habit of eating like you’re in training.

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  2. I definitely fall into this category !!! Not sure if it is genes/metabolic rate like the study says or more like the habit of eating like Janis mentioned above.
    However, I did find my way back into sports and totally enjoy it 🙂

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  3. I disagree that it stems from habit of eating more. I wrestled for 5 years and maintained an incredibly lean physique with little thought of what I ate during that time. Ten years later, I have to be extremely strict with what I eat just to maintain my weight, and I don’t eat even close to as much as I did back then, even though I am still very active and very fit.

    Thanks for the interesting post, Arya.

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  4. This is quite interesting and seems logical. However, I do take issue though with the following quote:
    “It also perhaps explains why so many of my patients can maintain rather high levels of physical activity once they find their way back into sports (for e.g. after bariatric surgery).”

    I don’t think the example was necessary in the statement. Even though you give it simply as an example, the fact that you chose to include the example implies that bariatric surgery or similar drastic action would be necessary for a fat person to be athletic. That’s simply incorrect. (The use of “e.g.” is also incorrect, but that’s a separate matter.)

    I hope this was simply a mistake and not an attitude you convey to your patients.

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  5. I am very much interested in the topic of why former athletes seem to become obese at a very high rate. I know that it takes a tremendous amount of discipline to become a competitive athlete and one doesnt lose that kind of discipline of mind and spirit as one gets older. So the increase in obesity in these subjects cannot be a result of decrease in discipline eg eating as one did during their training days. I would very much like to communicate with people who are experiencing the struggle with obesity who were formerly well-trained athletes. Please feel free to email me so we can communicate.
    Thank you
    Jennifer Green

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  6. I was watching the biggest loser show and was curious about why so many athletes become obese. I am not obese but have chronic fatigue and fibromyalgia, which is so much more debilitating than it sounds when severe. Lots of us, me included, were high performing athletes and/or high performing individuals before. I see a connection in the fact that over exerting the body over a long period of time results in severe reactions of over protection, may it be the shutting down of adrenals or over eating, for me right ther that’s the body trying to recover from extreme energy loss in the past. The way I see it, it is a reaction and not an action.

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