The key to sticking to a healthy diet this time of year is to avoid the all-or-nothing way of thinking, says Fleming. "Extreme dieting leads to continued patterns of bingeing and fasting, slowing your metabolism and decreasing the number of calories you burn every day," she explains.

A better strategy for controlling your weight? Make small, permanent lifestyle changes that you can maintain beyond the holiday season, like switching from soda to sparkling water or beginning your meal with fruits and veggies. "Unlike 'dieting,' embracing a healthy lifestyle has no starting or stopping point. It just means making good choices the majority of the time," Fleming says.

4. Don't Overdo Alcohol

Do you find sipping a celebratory drink makes you lose your willpower? You're not alone. "Alcohol tends to lessen your inhibitions, and you may find that you have less control over what you eat," explains Fleming. "If you must indulge in a holiday cocktail, consider diluting your drink with extra ice, water or seltzer, and alternating each alcoholic beverage with a glass of water in order to keep control of your eating and prevent dehydration."

Also, remember to count those liquid calories. A mixed drink, like a daiquiri or margarita, can have 500 calories per glass - that's almost a third of the total calories you should be consuming in an entire day!

5. Don't Forget to Start on a Positive Note

"Take 30 minutes and go for a walk the morning of your holiday gathering," says Fleming. By getting your exercise done early in the day, you're guaranteeing that you'll actually do it. Plus, working out early increases the odds that you'll watch what you eat from the very first meal of the day. "It's easier to make healthy food choices after you make this first healthy choice," says Fleming. "And the mood-boosting hormones that are released with exercise provide the added benefit of easing holiday stress and making you feel calm."