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ROBERT SIEGEL, host:

From NPR News, this is ALL THING CONSIDERED. I'm Robert Siegel.

MELISSA BLOCK, host:

And I'm Melissa Block.

If you have been piling on the pounds lately, especially around your middle, and if you're under a chronic stress and especially if you're a mouse, listen up. According to a study in the journal Nature Medicine, stress can lead to obesity - at least in mice.

Dr. Zofia Zukowska of Georgetown University's Department of Physiology and Biophysics led the research. Dr. Zukowska, welcome.

Dr. ZOFIA ZUKOWSKA (Chairperson, Department of Physiology and Biophysics, Georgetown University): Hello.

BLOCK: And let's describe this experiment a bit. You had, as I understand it, four groups of mice, two of which got a regular diet, two of which got a junk food diet, and then one group from each pair was subjected to stress. What kind of stress?

Dr. ZUKOWSKA: Well, we tried to make the life of mice a little bit more like the life of humans. So we subjected mice to two kinds of stress, one was they were standing in just a tiny little bit of ice cold water, like a puddle of ice cold water, a day for an hour, or another group was exposed to 10 minutes a day of aggressive alpha mouse.

BLOCK: An aggressive alpha mouse.

Dr. ZUKOWSKA: Yes.

BLOCK: It could be like the guy working next to you.

Dr. ZUKOWSKA: Uh-huh. It could be like a bad boss, yes, yes.

BLOCK: Well, what did you find in these mice in terms of their obesity?

Dr. ZUKOWSKA: Well, we found that if the mice were stressed and had high fat, high sugar diet, that combination and the only - that combination produced excessive fat accumulation around the belly. Within two weeks, there was, like, twice as much fat in the belly than normally. Well, all the other three groups, essentially, did not put on much weight and, in fact, the stressed mice on normal diet actually lost some weight.

BLOCK: And when you looked at those stressed fat mice, you discovered something in terms of their chemical composition and what was going on?

Dr. ZUKOWSKA: Yes. We found that in the biopsy of fat from stressed mice on high fat, high sugar diet, that they have elevated levels of chemical called your neuropeptide Y or NPY. That's a chemical that's released from nerves when nerves are activated by stress. We knew that from before that stress can do that, but we never knew that this would happen into fat in the constellation of stress and bad diet.

BLOCK: There's another interesting part of this, which is that in mice, you found that you could shrink the fat.

Dr. ZUKOWSKA: Yes. Well, soon as we have found how the body lays down fat, and we have found this Y2 receptor that's elevated, we decided to block the function of this receptor with another chemical that was fortunately available, at least for experimental use. And when this chemical was injected into the belly fat, again, within two weeks, the fat got melted away. About 50 percent of it has disappeared.

BLOCK: Dr. Zukowska, you know well that there are a lot of studies that show one thing in mice or other animals, and when you go to apply them in humans, either it doesn't work or it's really not safe.

Dr. ZUKOWSKA: Right. I think this situation is a little different because this, for years, have not worked in mice. Mice, when they are stressed, they lose weight. We have humanized, so to speak, the life of mouse, and by doing so we have repeated what happens in people. My observation from being a physician really suggested that there is a relationship between stress and obesity. So we're not talking about a phenomenon that's only present in the animal kingdom. On the contrary, it's the phenomenon that's present in the human kingdom. And we know that the same receptor and the same chemical exist in human fat.

BLOCK: You could say, and people will say, the thing to do is reduce stress and don't eat junk food.

Dr. ZUKOWSKA: Exactly. When you want to eat fatty food with lots of sugar, don't do it when you are stressed, if you can.

BLOCK: Well, Dr. Zukowska, thanks for talking with us.

Dr. ZUKOWSKA: Thank you very much.

BLOCK: Sophia Zukowska is chair of Georgetown University's Department of Physiology and Biophysics. She led the research into stress and obesity in mice that is published online in the journal Nature Medicine.

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