Study Offers New Insights into Obesity

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A new study shows that diet and exercise may not be the primary reason why obesity in America is growing. David Allison, of the University of Alabama, tells Debbie Elliot that there are other causes, including air conditioning, lack of sleep and a growing number of non-smokers.


We all know why Americans are getting fatter, or do we? An article in the International Journal of Obesity says that lack of exercise and an excess of junk food may not sufficiently explain our expanding waistlines. Air-conditioning, less sleep. Even older moms may be raising the obesity rate. All in all, the article looks at 10 unusual suspects. David Allison at the University Of Alabama Birmingham School Of Public Health was the lead author of the paper, and he joins us now.

Air conditioning is making us gain weight?

Professor DAVID ALLISON (University of Alabama Birmingham): Well, it is plausible. We know that when it gets very hot outside or inside, people tend to eat less. And so the more they are exposing themselves to air conditioning, which leads to cooler temperatures, the less their food intake will be reduced in the hot summer months.

ELLIOTT: Now, before we move onto the other factors how did you come to the conclusion that the big two, as you call them, were not enough of an explanation? It seems logical that couch potatoes eating junk food will gain weight.

Prof. ALLISON: When we reviewed the literature we first found that there were other factors that were almost certainly in play and that alone suggest that the big two cannot explain everything. But also we found that the evidence that the big two were in fact the overwhelming contributors was itself somewhat shaky. We found, for example, in research from the Rand Institute that the density of fast food outlets in areas was not necessarily correlated with how fat children were in those areas. So there were a number of studies of this type that led us to think that the big two were not sufficient explanations for the obesity epidemic.

ELLIOTT: Now, we don't have time to cover all 10 of your explanations. I think one that's a bit surprising is less sleep. You would think the more you slept the fewer calories you would burn, you would gain weight.

Prof. ALLISON: And indeed that might be true if in fact when you were awake you were out running around. But it may be that when people are awake they are sitting quietly watching TV. We know that if you deprive a rat of sleep, the rats begin to eat more.

ELLIOTT: Here's another one: the decrease in smoking in America.

Prof. ALLISON: We know that smoking is an appetite suppressant. We also know that smoking is a thermogenic agent, meaning that nicotine raises the rate of energy expenditure, metabolic rate. So those two things combined keep smokers on average a little bit thinner than nonsmokers. Now, we don't for a moment want to suggest that anybody should start smoking in order to lose weight. It is much better to be a nonsmoker who's a little bit fatter than a smoker who's a little bit thinner.

ELLIOTT: Dr. David Allison is a professor of biostatistics at the University of Alabama Birmingham. Thanks for speaking with us.

Prof. ALLISON: It was my pleasure. Take care.

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