MARY LOUISE KELLY, host:
Now, a lot of you today may be wishing your clothes have mysteriously shrunk. That would explain why they seem tight today, right? Couldn't possibly be that large Thanksgiving meal you ate.
Well, as a public service, NPR's Joe Palca has this explanation of what's just happened to your body. And Joe says there's some good news there.
JOE PALCA: With the help of Edward Saltzman, let's analyze the food that makes up the typical Thanksgiving dinner. Saltzman is at the U.S. Department of Agriculture's Nutrition Center, at Tufts University. He knows exactly what's in a turkey.
Mr. EDWARD SALTZMAN (Scientist, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University): Protein, a little bit of fat.
PALCA: How about stuffing?
Mr. SALTZMAN: Carbohydrates, fat, maybe a few vitamins and minerals.
PALCA: If you add peppers and some onions to the stuffing. Green beans?
Mr. SALTZMAN: Fiber, some vitamins, some minerals.
PALCA: Sweet potatoes?
Mr. SALTZMAN: Carbohydrates, fiber, carotenoids.
PALCA: Carotenoids are a source for the A vitamins.
Mr. SALTZMAN: Number of other vitamins and minerals.
PALCA: Okay. That's sweet potatoes. How about cranberry sauce?
Mr. SALTZMAN: Carbohydrates, mostly from the sugar they put in. Some vitamins, vitamin C.
PALCA: And let's not forget dessert, pumpkin pie.
Mr. SALTZMAN: Carbohydrate, fat.
PALCA: Fat from the pie crust.
Mr. SALTZMAN: Also some carotenoids, a few other vitamins.
PALCA: The healthy stuff is in the pumpkin part of the pie. Now, we need carbohydrate and fat and protein and vitamins and minerals in our diet. The problems come when you eat too much of them.
Unidentified Man: I can't believe I ate that whole thing.
PALCA: So what happens when you eat the whole thing, like at Thanksgiving dinner?
Mr. SALTZMAN: Your stomach is pretty elastic. It can accommodate a lot of food, basically by relaxing.
PALCA: But let's say somehow, we managed to eat five pounds of turkey and stuffing and pie and all. Will we gain five pounds?
Mr. SALTZMAN: Absolutely not.
PALCA: That's because our brains won't let us.
Roger Cone is at Vanderbilt University School of Medicine in Nashville, where he studies how we maintain our weight. He says our brains keep things in check.
Dr. ROGER CONE (Chairman, Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine): It's just like the thermostat in your house.
PALCA: If your weight goes up past the set point on the thermostat, your brain will take steps to see that you lose weight. It's not a perfect system.
Dr. CONE: People tend to gain maybe three-quarters of a pound to a pound over the holiday period.
PALCA: But taking off a sudden smallish increase in weight isn't all that difficult, especially when your brain is telling you it's the right thing to do. Cone says the problem with obesity in this country isn't caused by overeating at the holidays.
Dr. CONE: People have overeaten at Thanksgiving and Christmas and New Year's for years and years and years, even prior to the obesity epidemic.
PALCA: Cone says the problem is the pound or so we put on each year. That kind of slow weight gain has the effect of turning up the thermostat in the brain. And as a consequence...
Dr. CONE: If you lose weight, that sends an emergency signal to the brain. The brain thinks you're starving.
PALCA: Your brain fights to keep you at your higher weight.
Dr. CONE: A whole bunch of circuits get activated in the brain to increase your hunger, decrease your satiety, increase food-seeking behavior, even decrease your metabolic rate in order to preserve energy and get you back up to your previous fat level.
PALCA: Cone says it's a control system that's almost impossible to fight against.
Dr. CONE: It's like asking somebody to quit breathing. You can ignore the hunger signals, but the metabolic changes are completely subconscious and there's - they're physiological. There's nothing you can do about them.
PALCA: Bottom line, taking off long-term weight is a problem, but Ed Saltzman says the occasional holiday overindulgence just isn't that big a deal.
Mr. SALTZMAN: You certainly will not gain appreciable weight from overeating at one or two meals.
PALCA: Anything we can warn people about, or shall we just tell them to have at it?
Mr. SALTZMAN: I think that they should have at it. But when they're done having at it, they should go back to a prudent diet.
PALCA: You kind of knew that was coming.
Joe Palca, NPR News, Washington.
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