On the Nature vs. Nurture of Obesity

Highlights from the ongoing debate over the factors underlying the epidemic on pace to see 42% of Americans obese within the next 20 years.


In a head-to-head piece published yesterday in the British Medical Journal, Timothy Frayling, a professor of human genetics at the University of Exeter, argues that genetics outweigh (ahem) environmental factors as we look at causes of obesity. He cites research that has found adiposity between twins is concordant in up to 70 percent of cases. An obesity-related gene has also been identified; people with two copies of the so-called FTO gene are generally heavier compared to those without the gene variant. Moreover -- and not surprisingly -- sedentary people with the obesity-linked gene tended to be heavier than those with the gene who were physically active. Frayling concludes that our DNA may actually be far more responsible for human obesity than our surroundings. 

"An analogy can be made with smoking," Frayling writes. "If everyone inhaled the same amount of cigarette smoke every day, the strongest risk factor for lung cancer would be genetic susceptibility to the adverse effects of cigarette smoke." 

Not everyone is convinced, though. On the dueling end of the BMJ reports, John Wilding, a professor of medicine at the University of Liverpool, argues that although a great deal of propensity to develop body fat is inherited, the rate at which obesity is overtaking developed nations can't be explained on the basis of genetics. Ample supplies of calorie-rich food, combined with the decline of physically active lifestyles, has dramatically raised the likelihood of obesity in genetically at-risk individuals and indeed, for the population across the board. The significant uptick in obesity in recent years argues against a genetic cause.

Overall the daylight between these studies may not be that great. Frayling, the researcher arguing for genetics, says that because the FTO gene governs appetite, putting environmental cues in place to help reframe Americans' eating context will help them control their weight. Those findings would appear to agree with Wilding's conclusion that what surrounds us is a powerful determinant. 

Together, the BMJ papers add to a growing body of knowledge about the relative weight of the causes of obesity. While the research doesn't negate the value of a balanced diet or the need for exercise, it does suggest that extreme weight gain may be less of a choice than is often culturally regarded. Much in the way attitudes toward depression have changed over recent years, we may be coming to regard obesity as more of an illness than a personal shortcoming.
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Brian Fung is the technology writer at National Journal. He was previously an associate editor at The Atlantic and has written for Foreign Policy and The Washington Post.

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