If you're like many Americans, you're going to gain some weight over the holidays. But you may not gain as much as you think.
"People tend to gain maybe three-quarters of a pound to a pound over the holiday period," says Roger Cone, chairman of the Department of Molecular Physiology and Biophysics at Vanderbilt University School of Medicine.
He says our brains keep a tight rein on our weight. "It's just like the thermostat in your house," Cone says. If your weight goes up past the set point on the thermostat, your brain tries to slow down your food intake and tells you to start burning calories so you'll lose weight.
It's not a perfect system, and that's why we might put on an extra pound or so at the holiday. 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.
Long-Term Vs. Short-Term Weight Gains
Cone says the problem with obesity in this country isn't caused by overeating at the holidays.
"People have overeaten at Thanksgiving and Christmas and New Year's Eve prior to the obesity epidemic," he 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. As a consequence, if you do then lose weight, "that sends an emergency signal to the brain," Cone says. "The brain thinks you're starving."
So your brain fights to keep you at your new, higher weight.
"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 to get you back up to your previous fat level," Cone says. It's a behavior that's almost impossible to control.
"It's like asking someone to quit breathing," he says. "You can ignore the hunger signals, but the metabolic changes are completely subconscious, and there's nothing you can do about them."
Bottom line: Taking off weight gained over a period of years is tough, but the occasional holiday overindulgence just isn't that big of a deal.
"You certainly don't gain appreciable weight after one or two meals," says Edward Saltzman, a scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.