Life is full of uncertainties. Will you find true love? Will you get a tax refund? Will "Moonlighting's" David and Maddie ever get married?

One thing's for certain, thank goodness, and that's the approach of National Nutrition Month, which kicks off on Tuesday.

This year's theme is "Choose Good Nutrition: For Today and Tomorrow." And in conjunction with the occasion, a number of area registered dietitians will be taking their nutritional messages into restaurants.

Why restaurants? "More and more people are eating more and more of their meals away from home," explains Shirley Blakely, chairman of the District of Columbia Metropolitan Area Dietetic Association's public relations committee.

According to the most recent estimates provided by the National Restaurant Association, the average individual, age 8 or older, consumes 3.7 meals per week outside the home; lunch is the meal most likely to be eaten away, and singles are the most frequent diners out, tucking in an average of 4.3 meals outside the home per week.

So it seems fitting that restaurateurs should participate in celebrating National Nutrition Month. Throughout March, in fact, about a dozen local eateries plan to host registered dietitians, who will be on hand to discuss with patrons their nutritional concerns and offer advice on healthful menu selections. As of press time, participants include Tony Lin's Kitchen (Rockville) Clyde's of Tysons Corner, American Cafe (in Georgetown), Old Ebbitt Grill (Washington), Blackie's House of Beef (Washington), Hyatt Regency (Bethesda), El Torito (Washington) and Hyatt of Capitol Hill (Washington). For specific times and dates, contact the individual restaurants.

Meanwhile, from area registered dietitians, here's a brief soup-to-nuts primer for dining out healthfully:

Cocktails: Opt for club soda, sparking water with a twist, a wine spritzer (which contains about half the calories of a glass of wine) or nonalcoholic beer. "Think in terms of calorie trade-offs -- would you rather have a cocktail or dessert?" suggests Lolita Kaul of Howard University's College of Medicine.

Appetizers: Opt for starters, such as clear soups (but watch the salt) and seafood cocktails with a twist of lemon (skip the tartar sauce). Take a single roll from the bread basket and request that the basket be removed from the table (that goes for leftover entrees, too). Salad dressings (oil and vinegar is one of the best bets) should be served on the side. Ditto gravies and sauces.

Entrees: Generally, the paler the meat, the less fatty it is likely to be; Ask for meats to be broiled, grilled, roasted or poached, and then trim any visible fat before eating. Depending upon their preparation, poultry and fish dishes are even better bets -- cold-water fish, such as cod, haddock, flounder, herring and sardines, are high in the type of fat known as Omega-3, which is shown to be beneficial in lowering cholesterol, notes dietitian Shirley Blakely. Learn to season dishes with lemon, pepper and hot pepper sauces instead of salt and butter.

Ask for vegetables to be steamed rather than saute'ed; if given a choice, choose baked potatoes over French fries, and request yogurt instead of sour cream as a topping. And eat your vegetables first to get a sense of satisfaction (this will also limit the tendency to overeat). At a buffet, select small portions and skip the fried foods.

Dessert: If possible, choose fresh fruit or, as an ice cream substitute, a sorbet. If you must splurge, consider splitting a dessert with a companion.

Dining out doesn't mean you have to sabotage a diet or wreak nutritional havoc on your body. In a Gallup poll conducted for the National Restaurant Association two years ago, almost all operators surveyed said they offered diet drinks and sugar substitutes. More than eight out of 10 offered decaffeinated coffee, and about two-thirds stocked margarine as well as whole-grain bread, rolls or crackers. Moreover, almost three-quarters of the respondents said they would be willing to alter preparation methods upon request.

In the end, though, it's up to the diners to make the proper food choices. "Consumers might be reluctant to make special requests, but they shouldn't be," advises Claire Regan of the National Restaurant Association. After all, she adds, "restaurants are in business to serve the public."

Here's a step in the right direction, from Executive Chef Penny Boucher of the Old Ebbitt Grill:

Express Lane list: fresh tuna (or other firm-fleshed fish), tomatoes, olive oil, wine vinegar, fresh garlic, coriander OLD EBBITT GRILL'S GRILLED TUNA WITH FRESH TOMATO VINAIGRETTE (2 servings)

2 7-ounce tuna steaks, about 1/2- to 3/4-inch thick (or substitute another firm-fleshed fish)

2 large vine-ripened tomatoes, peeled, seeded and chopped

4 tablespoons olive oil

4 tablespoons wine vinegar

1 teaspoon fresh garlic, minced

2 tablespoons fresh coriander, chopped

Freshly ground black pepper to taste

Grill the fish under a broiler, about 3 minutes per side, or until firm to the touch. In a bowl, combine tomato, olive oil, wine vinegar, garlic and coriander. Ladle sauce over grilled fish. Season with freshly ground black pepper and serve warm.