Waistlines and credit cards seem to reach their limit during the holidays, and it takes superhuman effort to keep the two in hand. Although the wishes of loved ones will remain costly, the effects of a party-happy appetite can be restricted. This doesn't mean hibernating in bed until New Year's with lips pinned shut, but it does mean a few well-kept resolutions.

It all starts with a realistic attitude. This is not a time to begin a diet. We are after maintenance, here, not a drop of twenty pounds. When at a party, the place to stand is not right next to the buffet, obviously. But avoidance of fat can be more creative: You can wear shiny bright lipstick that you don't want mussed, a hat with a veil or funky silk gloves. Those men who don't like these last ideas can exercise by bringing in the fire wood all night.

But if you find this too much effort, you are going to have to plan ahead.

Execise before you go out, not the next morning. First, it will help curb your appetite and second, who's kidding who about getting up the next morning?

Try to get plenty of rest. Exhaustion causes jitters and jitters cause compulsive snacking.

Mary Dickie, a registered dietician working for Group Health Association and also a private nutrition consultant, discussed the problems facing her patients during the holidays.

"It's not Christmas that kills people, it's that a lot of them started celebrating before Halloween and won't stop until New Year's. There's always a special occasion; it's somebody's birthday, it's a holiday, somebody's leaving at the office, someone going on vacation."

There are important things to keep in mind, she says, to help you maintain your weight during these strenuous times.

Do not go to parties starved; eat a light snack just before you go, to curb your appetite.

Eat what you like, and only what you like. It is not mandatory to eat the turkey just because you want the stuffing.

Watch the calories in beverages; the calories lurking in eggnog are enough to make you choke. Scotch and soda and wine spritzers are much lighter choices.

When at dinner, eat a little of everything to taste, not to stuff yourself.

Plan non-food activities for your family; instead of baking cookies, go ice skating, instead of trundling everyone in the car to get ice cream, go bowling.

Plan ahead carefully to set up your exercise program; if you are going away to relatives and can not attend your regular exercise class, don't use that as an excuse not to exercise, go for a brisk walk instead.

Variety in your food is very important; a diet of baked chicken every day will last but one day. Try steamed shrimp, fresh fruit, frozen fruit, exotic vegetables like artichokes, celery root, asparagus, red and yellow peppers.

The important thing is to not feel deprived, especially during the holidays. Eat low-fat foods that seem like treats: sole, scallops, oysters, monkfish, salmon. Even nibble french bread on the side; it has no fat. And finish the meal off with bright fruit sorbets.

If there's a party that's sure to beat your will power, compensate by eating light earlier in the day and the day after.

"I tell my patients that if they did better than last Thanksgiving or last Christmas, then that's a success. If they had one less piece of cake this time, then they have improved. It will certainly help them from gaining weight."

Here is a recipe with a creamy sauce and an elegant look. Make it for yourself between parties or serve it to your friends at your own party -- just don't tell them it's good for them and low-calorie or they'll insist on a pizza for dessert. With salt and pepper in your cupboard, it will take a only a few minutes in the supermarket.

EXPRESS LANE: cucumber, red snapper, limes, yogurt, dijon mustard, chives or dill, carrots, fresh ginger RED SNAPPER WITH CUCUMBERS (6 servings)

This easy-to-make dish has only 165 calories per serving.

1 large cucumber

1 tablespoon salt

1 red snapper, filleted (about 2 pounds)

Juice of 2 limes

1/2 cup yogurt

1 teaspoon strong dijon mustard

2 tablespoons chopped fresh chives or dill plus extra for garnish

Salt and pepper to taste

Wash the cucumber and slice very thin. Sprinkle with salt and set aside on a plate so that the cucumber sweats out its water. Drain before using.

Wash the red snapper fillets and pat dry. Place them in a steamer and steam, covered, for 5 minutes or until barely done. Remove carefully to a platter, pour the lime juice over them, and set aside.

In a bowl, mix together the yogurt, mustard, and chives or dill. Add salt and pepper to taste. Mix well.

Arrange the fish fillets on a platter, cover with the sauce, and surround with cucumber slices. Sprinkle with chives and serve at room temperature. From "Colette's Slim Cuisine," by Colette Rossant (William Morrow & Co., New York, 1983) CARROTS WITH GINGER (6 servings)

Bright and full of flavor, this dish masks well its scant 50 calories per serving.

3 cups carrots, sliced on dias

1 tablespoon grated fresh ginger

Salt and pepper to taste

Steam the carrots until tender. Mix with ginger, salt and pepper and serve.