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Obesity: Nature & Nurture, But How Much of Each?

Dueling studies published in the British Medical Journal ask whether genetic or environmental factors are more influential when it comes to extreme weight gain.

What’s the Latest Development?

A new study published in the British Medical Journal argues that genetic factors outweigh environmental ones when it comes to obesity. Timothy Frayling, author of the study and University of Exeter geneticist, has found that twins have similar body fat ratios in up to 70 percent of cases. “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.” 

What’s the Big Idea?

An opposing study, published the same day in the same journal, 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.” The substantial uptick in obesity in recent years, particularly in the first world, seems more easily explained with reference to ample supplies of calorie-rich food combined with the decline of physically active lifestyles. Still, new evidence suggests that extreme weight gain may be less a matter of choice than is culturally believed.

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