Last week's dieting in restaurants column promised nothing in terms of weight loss (if it didn't shave a few pounds off you, call your doctor, not me). It did, however, promise the second half of my adventuring with the Scarsdale Diet in restaurants. As I prefer to do when dieting, I saved the best for last. Fish

Every day should be Friday, for fish days are among a Scarsdale dieters happiest. Of course, you will have to eat the recommended protein toast at home, but look what main courses you have to choose: The brand-new La Maree, 1919 I St. NW, was most understanding. The waiter, obviously a fellow dieter, was full of suggestions. He disapproved of my eating tomatoes ("full of sugar"), but put real thought into my choice of broled fish. After I selected one, he returned to tell me that the kitchen had just received fresh swordfish, and I must try that. Right he was. My salad was a decorative little thing, concentric circles of tomato and spinach, but I could have had endive and watercress (salads $2.25 at lunch; I had switched my Scarsdale lunch and dinner that day). The fish ($6.25) was exquisite, two slices of swordfish pounded as thin as veal scallops, very soft and velvety and slightly smoky from a charcoal grill. There was a touch of butter on the fish, but I was too delighted to complain. I removed the grilled tomato with crumb toppping and the boiled potatoes, ventured a taste of the creamed spinach that was nearly fatal to my diet, and enjoyed each morsel but still felt hungry, at least until my appetite was killed by the grotesquely bitter espresso. The waiter told me to come back again when my diet was over. I will.

A comparable welcome was at Nora's, 2109 R St. NW. I called on a chicken day to check the menu. The person who answered described the day's chicken special but it was unsuitable. He suggested, "Catch us on day 13," because the cold poached fish with dill was a beauty.

Dieting is a good excuse to go to Joe and Mo's, 1211 Connecticut Ave. NW, if you need an excuse. It costs non-diet prices, for two diet dinners ran nearly $50 after tax and tip. But the doggie bag turned it into another meal, and the valet parking must have saved a couple of bucks. Joe and Mo's, of course, is a natural for steak days. But I prefer it for fish days. No, the wonderful pumpernickel and rye breads will not substitute for your thin protein toast, so get those off the table immediately. Start with sliced tomato and onion salad. The red tomatoes alternating with purple onions on a curly green endive bed is an artistic beginning. It definitely beats the tired tossed house salad, particularly without dressing to perk it up. A squeeze of lemon and a grind of pepper should accent it. Next, a grilled fish filet -- salmon, swordfish. rockfish, snapper -- or, as the greatest challenge to the kitchen, sole. The filets are moist and fresh, grilled so that the surface is crusty and golden, highly seasoned with paprika. The flesh is juicy, sea-sweet. Delicious. Enormous. With it, an order or broccoli or green beans (without butter, and hold the hollandaise) is enough to keep you munching for a week. The niceties -- half a lemon with peel curled into ringlets, the solicitous and witty service -- almost compensate for the potato pancakes you are missing. The meal at least feels hefty and certainly looks lovely. For dessert another treat, half a melon zig-zag cut to look indeed like a dessert, or fresh strawberries. A cup of good coffee. See how easy dieting is? Fruit Salad

Rating low on the food chain has its financial advantages, but requires some understanding of restaurant economics. The price of a single dish -- a plate of fresh fruit, for example -- can seem exorbitant if you break down the cost by the price of fruit. But you must calculate also the cost of the location, the space, the furnishings and the service. Lunch at Le Consulat in the Embassy Row Hotel, 2015 Massachusetts Ave. NW, is not cheap, but a diet lunch is cheaper than a full meal with wine, and all the externals are included in the price. Thus, a fruit lunch ($5.75 plus beverage, tax and tip) comes with a beautiful sunny room overlooking Massachusetts Avenue grandeur. It includes solicitous service and leisurely enjoyment of the space. It takes place at a table set with elaborately folded napkins and handsome tableware, the table surrounded by the luxury of space. The fruit plate comes with cottage cheese, frozen yogurt and strawberry dressing, all of which you should do without on the Scarsdale diet. It is no deprivation, for the large oval plate is arranged with succulent beautry: a half pear and apple thinly sliced and reformed to look whole, three kinds of melon, whole strawberries, bunches of grapes in two colors, banana (which you can readily leave). Picking among the fruits and nibbling can occupy a pleasant hour. Another diet alternative, equally appetizing, is a seafood platter of raw oysters, cold scallops and king crab legs, shrimp and some less than desirable mealy mussels, presented with a gift-wrapped lemon half and pickles and olives. At $8.95, it, too, encourages unhurried pleasure.

The Eatery in White Flint Mall hurries you through your pleasure, and its Body Shop stand's fruit plate ($2.40) looked vapid with a small slice of watermelon, eight cubes of green-edged cantaloupe, five squishy strawberries and seventeen withered grapes. Unsavory looking, it was not nearly as good a buy as the Consulat's $5.75 fruit plate. And you pay for the inferior frozen yogurt that is supposed to come with it, whether you get it or not. Ask for it in a separate dish and offer it to some undiscriminating child for dessert. The Body Shop's menu lists calorie counts of its foods, which encouraged people in line to note, "Everybody talks about a diet, but nobody is on one." No wonder.

But the frustration of eating out on fruit salad days is easily avoided, at least on sunny days. Downtown, lunch in the most attractive surroundings, with no harassment from servers and no garbled orders. That is the picnic in the park. Buy a few pieces of fruit from a vendor for under a dollar. Park yourself on a bench. Feel ounces and tensions melt away with each bite, and enjoy the fact that this may be the only lunch spot in town where you can get a ripe pear or a pomegranate. No burger-on-a-bun and french fries can compete with that.