"But wait a bit," the Oysters cried "Before we have our chat "For some of us are out of breath "And all of us are fat." From "The Walrus and the Carpenter," by Lewis Carroll

Whatever the root cause of overweight, excess fat is, in the end, the result of too many calories and too little activity. Mild obesity, by itself, with no other complications, is not a major risk factor in heart disease. But the odds change when obesity is pronounced (30 pounds or more overweight), which puts an added strain on the circulatory system.

When overweight is accompanied by high blood pressure, high blood cholestrol, diabetes or cigarette smoking, the risk is much greater even if the degree of overweight is not significant.

In addition, overweight, or more strictly speaking, obesity may promote high blood cholesterol, hypertension or diabetes in individuals who have an inherited tendency to these conditions.

Between one-fifth and one-third of the 23 million Americans with high blood pressure have been estimated to be markedly overweight, and about 80 percent of the 10 million or more diabetics are overweight.

In the early stages and in mild cases of diabetes and high blood pressure, weight reduction, especially when combined with regular exercise, may lower blood pressure and usually improves glucose tolerance (the body's ability to deal with blood sugar). In all cases, weight reduction and exercise, under a physician's direction, are advisable.

Calorie control and weight reduction (on a sensible diet) when it is necessary are important aspects of the anticoronary diet. But do let me point out that conrolling weight, however drastically, is not the whole story.

Being thin is not a guarantee; indeed, many reed-slim people have high blood pressure, high blood cholesterol and heart attacks.

If you control your weight through a high meat or egg diet, you may be doing yourself more harm than good, since lowering cholesterol is generally more important than simply losing weight.

Still, weight control is an essential part of an anticoronary program. Children and adolescents need enough calories for normal growth. Adults should try to stay at approximately what they weighed in their early 20s, provided they were not obese then. And at no age should we let excess calories run to fat. Both control of caloric intake and the maintenance of an adequate level of daily exercise should be used as fat prevention.

By cutting down on the total fat in your diet, you already have a head start at calorie control, replacing foods high in fat at 270 calories per ounce with those high in protein or carbohydrate (other than sugar) at 120. In addition, to using more lower-calorie fish and poultry, consider substituting main dishes made with dried beans and peas or whole grains for meats several times a week.

Most people gain weight not in one grand binge of overeating but in tiny increments of a few unused calories each day. One small 100-calorie bar of chocolate as a snack every afternoon can add up to 10 extra pounds of fat at the end of the year. Therefore, it is a good idea to plan menus to get the most nutrients for every calorie. Keep high-calorie junk foods out of the house.

As many of us know, habits are hard to break. Therefore, don't train your children to overeat by insisting that they clean their plates when they are no longer hungry. This may push them toward overweight. Teach children to take helpings small enough that they are sure to be eaten. Seconds, if wanted, will be requested.

But don't let them pass up the nutritious main course and then gorge themselves on an immense, sugary desert. One way to prevent that is to exclude high-calorie, low-nutrient desserts from the menu. Instead, serve reward. That will only condition a child to think of sweet, empty-calorie foods as nutritionally or socially superior.

The following menus and recipes, prepared by dietitian Jeanne Goldberg, are suggested for days three and four of a 10-day diet plan. DAY 3: Breakfast Orange juice Shredded wheat with skim milk Toast with margarine Coffee with skim milk Lunch Lentil soup with frankfurters Salade Nicoise French bread with margarine Fresh fruit Tea or coffee Afternoon Snack Fresh fruit Dinner Garlic lamb, Catalan style (recipe below) Steamed rice zucchini Raw vegetable sticks Bread with margarine Baked apple Tea or coffee Evening Snack Toasted English muffin with margarine DAY4: Breakfast Orange juice Farina with skim milk Whole-wheat toast with margarine Coffee with skim milk Lunch Flaked fish salad sandwich with Russian dressing Tomato wedges and pepper rings Fresh fruit Tea of coffee Afternoon Snack Fresh fruit Dinner Veal stew with white onions (recipe below) Noodles Broccoli Tossed salad with vinaigrette dressing Bread with margarine Grapefruit half Tea or coffee Evening Snack Raisin biscuits Skim milk GARLIC LAMB, CATALAN STYLE (10 servings) (360 calories per serving) 1 boned lamb shoulder (about 3 pounds) 2 tablespoons oil 1 thick slice (1/2 pound) lean raw ham 1 large onion, sliced 1 large carrot, sliced 2 tablespoons flour or 1/4 cup bread crumbs 1 cup dry white wine 2 cups mean stock or consomme 12 medium-size cloves garlic, unpeeled 2 sprigs parsley or some fresh sweet basil leaves or pinch dried basil 1 bay leaf 1 piece dried orange peel Salt

Trim all external fat from lamb. Roll and tie it. Heat oil, add lamb, ham, onion and carrot. Cover and cook slowly for 30 minutes. Lift meat out. hPour off half the fat; brown flour or bread crumbs in remaining fat. Dice ham and return it and lamb to pot. Add wine, stock or consomme, garlic, parsley or basil, bay leaf, orange peel and salt. Cover and cook slowly 1 hour or until lamb in tender.

Chill. Discard fat that congeals on top and reheat. To serve, lift out lamb, untie it and place on platter. Pour sauce over. Veal stew with white onions (4 servings) (350 calories per serving) 1/4 cup flour Salt and pepper Paprika 1-1/2 pounds veal shoulder, well trimmed and cubed 2 tablespoons oil 1 onion, minced 1 teaspoon thyme 1 cup white wine 12 small onions, peeled

Combine flour, salt, pepper and paprika in brown bag. Wipe veal cubes dry. Place in bag a few at a time and shake lightly to coat with flour. Heat oil. Brown veal quickly on all sides. Drain any grease in pot. Add onion, thyme and white wine. Simmer until tender (about 1 hour), adding water if sauce becomes too thick. Add onions and cook until tender (about 10 to 15 minutes).