'TIS THE SEASON for twinkling yuletide lights at the Old Post Office, the White House Christmas tour and red velvet ribbons adorning Georgetown shops. 'Tis also the season for eating 'til you're as stuffed as the turkey at your Christmas dinner table.

I don't want to be the Grinch who stole Christmas dinner, but I also don't want to see all your hard workouts go down the drain because you can't just say "no" to holiday treats. You can stay slim during the fat season. You don't have to start 1988 with 5 or 10 extra pounds around your middle.

Your first step: Becoming aware that December's over-indulgences really can undo all your miles of running, hours of aerobics classes and revolutions on your bicycle.

For example, if you think one beer at your office Christmas party won't really hurt, you should know that 8 ounces of brew contains approximately 114 calories. Sweating off every one of those nasty calories will take the average person 43 minutes of bicycle riding at 6 mph, 32 minutes of walking, 17 minutes of running at 5 mph or 14 minutes of swimming at 2 mph. If, at the same office party, you have a shot of 100-proof whiskey, you're gulping 122 calories. Working it off will take 46 minutes of biking, 34 minutes of walking, etc.

And that's the good news.

High calories aren't limited to alcoholic beverages. A cup of cocoa made with milk has 232 calories and will take the average person 88 minutes of biking, 65 minutes of walking, 31 minutes of running or 28 minutes of swimming to work it off.

Just one chocolate Christmas cookie packs a walloping 93 calories. Compare that to the healthy orange in the toe of your Christmas stocking. It's just 72 calories and takes 27 minutes of biking, 20 minutes of walking, 10 minutes of running or 9 minutes of swimming to work it off.

When you sit down for Christmas dinner, just 4 ounces of turkey contains about 216 calories. You'll work it off after 82 minutes of biking, 60 minutes of walking, 29 minutes of running, or 26 minutes of swimming. If your turkey just isn't complete without gravy, be aware that two tablespoons have 82 calories and will take you an extra 31 minutes of biking, 23 minutes of walking, 11 minutes of running or 10 minutes of swimming.

Of course, part of the fun of Christmas is found in sharing seasonal foods with friends and family. Don't feel like you can only crunch celery while everyone else is filling up on goodies. Just keep these statistics in mind whenever you feel like asking for seconds.

But if your Christmas cookie craving won't go away, go ahead and indulge. If you don't give in to a strong craving, a few days later, you might find yourself gobbling the contents of an entire cookie jar instead of the one cookie that would have satisfied you a couple of days earlier.

Another stay-slim technique is to make time for working out. Yes, it's tough when you've got cards to mail, presents to wrap and trees to trim. But studies show exercise really curbs your appetite.

Also, after a feast, relax for at least 30 minutes and then get family members to join you in an after-dinner walk. A short (20-minute) brisk walk will get you feeling more energetic after a big feast and also helps your body digest everything you couldn't resist.

Then, after New Year, we'll work it all off.