Any way you muscle it, physical activity is essential to your effort to hold the line against holiday weight gain. From the National Weight Control Registry (an ongoing study of successful "losers" who have dropped 60 pounds and kept them off for an average of five years) to the Diabetes Prevention Program (a federally funded project showing that weight loss can help delay type 2 diabetes), study after study shows that regular physical activity helps to prevent weight gain.

Still not convinced?

Take a look at these findings from a National Institutes of Health (NIH) study of 195 people conducted from Thanksgiving to New Year's. The study, led by Jack Yanovski, head of the unit on growth and obesity at the National Institute of Child Health and Human Development, and published in the New England Journal of Medicine in 2000, found that many things had no impact on holiday weight management. Among them: dieting before the holidays, the number of holiday parties attended, stress levels, changes in smoking habits and depression.

What did count? How hungry people reported feeling during the holidays: Those who reported feeling less hungry actually lost a little weight. But as Yanovski notes, "you can't do much about that."

What else mattered? Physical activity. "Those who described themselves as being much more physically active [than usual] actually lost weight during the holidays," Yanovski said. But even people who just reported being somewhat physically active "didn't lose weight and didn't gain weight," he said. "Their weight stayed stable."

Here are some ways to help you work more physical activity into your day as the holiday season kicks into high gear:

Schedule active get-togethers. Think ice skating, sledding, caroling parties, cross-country skiing, long walks, museum outings -- anything that keeps you moving rather than sitting and eating. "This is an opportunity to work on changing some of your family traditions for the holidays," said registered dietitian Bonnie Jortberg, program director of the Colorado Weigh, a weight loss program at the University of Colorado Health Sciences Center in Denver.

Set realistic exercise goals. Okay, so you vowed to work out out five times this week and only made it to the gym twice. "Very often people need to lower their expectations about the amount of physical activity they can get during the holidays," said Marsha Hudnall, director of nutrition and eating behavior programs at Green Mountain at Fox Run, a Vermont spa. Better that than concluding you've failed and giving up. "Maybe you shoot for three times a week and get there one to two times. Instead of feeling bad, scale back. . . . Even five to 10 minutes will help."

Take the stairs. Yup, you've heard it before, but hoofing it up and down the stairs remains one of the basic "lifestyle" exercises that can really boost your daily activity level with minimal time commitment. So rather than waiting in line for the elevator, take the opportunity to find the stairs. (A 150-pound person will burn about 25 calories for every five minutes of stair climbing.) Or make the stairs part of an "indoor" exercise circuit at your home or office. When possible, walk up the escalators rather than standing. And instead of loading up for one big trip up and down stairs at home, take smaller loads so you make multiple climbs. It was that kind of strategy that helped folks in the NIH study maintain their weight. Other effective lifestyle exercises include parking at the far end of the lot; getting off the bus or Metro a stop early and walking the rest of the way; and walking or biking to errands.

Be flexible and creative. Dance to holiday music at home. Do housework to music with a beat. Stretch while wrapping presents on the floor. "You can build in activity even when doing all the kinds of things that we do around the holidays," Yanovski said.

Log your daily activities. Use a journal to keep track of your activity or record it online for free at www.fitday.com.

Lift weights. It can take only minutes and pays off by boosting your metabolism for the next 24 hours, according to William Kraemer, professor of kinesiology at the University of Connecticut. And studies show that weight training helps people of all ages and physical conditions improve strength. A new study by Tufts University researchers published in the December issue of Diabetes Care finds that weight lifting even helps improve blood sugar levels in older adults with type 2 diabetes.

-- Sally Squires

Caroling? Mall walking? Ice skating? Weight lifting at your desk? How are you burning calories during the holiday season? Share your tips -- or ask any nutrition question -- when Sally Squires hosts the Lean Plate Club, our weekly online chat about healthy eating and exercise, from 1 p.m. to 2 p.m. today at www.washingtonpost.com. The latest goals for the Holiday Challenge are in this week's Lean Plate Club electronic newsletter. To subscribe, log on to: www.washingtonpost.com/wp-srv/email/front.htm. And yes, the subscription is still free.