10 More Possible Triggers to Obesity

10 Factors in Rise of Obesity

1. Inadequate sleep — average amounts of sleep have fallen among Americans, and many studies tie sleep deprivation to weight gain.

2. Increased consumption of endocrine disruptors, substances in some foods that may alter fats in the body.

3. Climate-controlled environments. Air conditioning and heating limit calories burned from sweating and shivering.

4. Decrease in tobacco use. Smoking is often linked to appetite suppression.

5. New prescription medicines that promote weight gain.

6. Changing demographics — there are now more middle-aged and Hispanic Americans, groups that have higher obesity rates.

7. Women giving birth at an older age, which correlates with heavier children.

8. Genetic influences during pregnancy — a so-called "fetally driven positive feedback loop."

9. Natural selection — heavier people tend to survive tough times better than skinnier humans.

10. Assortative mating, or "like mating with like" — meaning heavier people procreate with others of the same body type, gradually skewing the population toward the heavy end.

Source: International Journal of Obesity

New research suggests that lack of sleep and environmental toxins are just as likely to cause obesity as eating fast food or failing to exercise. Dr. Sydney Spiesel, a Yale Medical School professor and a contributor to Slate, talks with Madeleine Brand about new research that lists other possible causes of obesity.

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MADELEINE BRAND, host:

From NPR News, this is DAY TO DAY.

No one doubts that Americans are getting fatter, as we hunker down behind our desks all day, and eat super-sized orders of fries. According to new research, though, fast food and a sedentary lifestyle may not be the only contributors to the growing problem of obesity.

Dr. Sydney Spiesel, of the Yale Medical School, joins us regularly to talk about medical research. And, Dr. Spiesel is also a contributor to the online magazine, Slate.

Hi, Syd.

Dr. SYDNEY SPIESEL (Doctor, Yale Medical School): Thanks. Always nice to be here.

BRAND: So tell us about the researchers and how they came up with this.

Dr. SPIESEL: There really is, truly, an epidemic of obesity. And the two reasons that always seem so clear to everybody, is that it has to do with increasing availability of food, and fast food, and lack of exercise.

This study, which was put together by 20 eminent researchers around the country, on obesity and on the causes of obesity, led by David Allison of the University of Alabama.

They didn't reject these two. But they're saying, Well, wait a minute, are there other things that might be equally important in contributing?

And they came up with a list of 10, although they said there are even more.

BRAND: And we are all on the edge of our seats, wanting to know what those 10 are.

Dr. SPIESEL: Well, you probably don't want to hear all 10, because it's a long list, but let me tell you some of them.

Sleep deprivation, for example, is one.

BRAND: Something I know well, yes.

Dr. SPIESEL: Yes. Well, we all know it well. In the last - I don't know how many years, I'm guessing, maybe 50 years - there's been a drop, for adults, in sleep. We've gone from an average of about nine hours a night, to an average of about seven hours a night. And it turns out, that both in humans and in animals - this has been actually very well documented - sleep-deprived animals and sleep-hungry people, turn out to be hungry for more than sleep. It really, quite impressively, increases the amount of oral intake that people induce(ph).

It's not just a matter of the extra time being awake, that there is something about being tired that seems to contribute. So that's one thing.

Let's see. Some other things. There are a lot of materials in our environment, especially things - chemicals, that leach out of plastics - that we now know, become part of our food, and many of them have hormone effects. They behave like female hormones, estrogens, or they - some of them block androgens, male hormones. And all - both of those properties cause weight gain.

A lot of the medications that we're taking. You know, everybody's now taking psychoactive medications, anti-depressants, other mood-stabilizing drugs. The number of prescriptions for these is just extraordinary. And almost every one of them, even medications used to treat diabetes and used to treat blood pressure - almost all of these lead to weight gain.

You know, these researchers say, we don't know. We don't know whether these are playing a significant role. But there's at least as good evidence for these things, as there are for the big two that we've previously been focused on.

BRAND: And it's possible, maybe even probable, that all of these things come to play in a single person.

Dr. SPIESEL: I think that that probably is true. That we don't know. And it may be that one is more important than another, but I think it really is true.

BRAND: So those were just a few other factors, besides diet and exercise, that may be contributing to the epidemic of obesity in America, and you can find all 10 at our website, NPR.org.

Thanks a lot, Syd.

Dr. SPIESEL: My pleasure.

BRAND: Opinions from Dr. Sydney Spiesel. He's a practicing pediatrician and a contributor to Slate.com.

More coming up on DAY TO DAY on NPR News.

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