That's because fidgeting burns calories -- as many as several hundred a day. And since you probably won't eat fewer treats during the holidays, it's time to start thinking about how you're going to move more.

We're not talking about extra trips to the gym, and nobody expects you to get buff by January. But add some effort to your daily routine and you might also be able to add that second slice of fruitcake.

One reason so many people gain weight this time of year is that they focus only on what not to eat while ignoring what they should be doing -- anything that ups their physical activity.

Something as simple as a 10-minute walk -- even at the mall -- can burn as much as 100 calories. And researchers have found that people who remain active during the holidays are the least likely to gain weight.

"That suggests you can get away with eating the way you want to if you continue exercising," said Amy O'Connor, deputy editor of Prevention magazine. "The problem is you stop exercising and you overeat."

Take it one step at a time, literally, says Ann Yelmokas McDermott, a nutrition scientist at Tufts University. Park your car at the far end of the lot, skip the elevator, and carry your bundles to the car -- it's cardio- and weight-training in one.

And even though your shopping schedule may be squeezing your workouts, she urges you to keep your date with the gym. Even shortened or lethargic workouts are better than sitting in front of the television.

Changing around your usual fitness routine can help, too. If you normally use a stationary bike at the gym, instead be a bit more seasonal -- pack up the kids, rent some skates and head to the rink or a nearby pond.

Even buying a Christmas tree can be a workout. Most farms that let you cut your own require you to tromp through the woods in search of that perfect evergreen. Nothing like a hike on a cold day to burn calories.

Dr. Robert Kushner, a professor of medicine at Northwest University, encourages people to use the increasingly ubiquitous pedometer to track their daily steps and motivate them to take more.

"It gives people a sense of control on how to burn calories," he said.

O'Connor's favorite suggestion for getting motivated to get moving is a daily look in the mirror. Naked.

Mike Ryan, a spokesman and trainer for Gold's Gym, thinks of holiday fitness as part of a contract with yourself. Sort out in advance how you will behave (including indulgences) and how you will deal with that.

Make the contract specific. For example, decide that for each slice of pie you will do two laps around the block or 30 minutes of fast-paced shopping at the mall. This lets you indulge without guilt because you have a plan for dealing with it.

But make sure your contract doesn't contain the I'll-wait-until-January clause. Ryan says few things doom a diet like a month or two of no-holds-barred eating.

It also helps to think of food in terms of activity. Equate treats with the effort needed to burn them off and you might be less tempted to indulge. Or you'll at least know what's in store for you tomorrow.

Want a slice of pumpkin pie? Feel like swimming for 50 minutes? A sugar cookie is easy -- 20 minutes of yoga should do the trick. But a cup of stuffing will have you shoveling snow for 40 minutes.