For anyone on a special diet -- low salt, low calorie, low fat, low carbohydrate--celebrating a birthday can become a matter of either denial or capitulation, a choice of just another grilled fish or of sabotaging your body.

We challenged two of Washington's top culinary talent to provide a dinner extravagant enough for a celebration, yet suitable for a diet. Gabriel Aubouin of La Brasserie and Jean Louis Palladin of Jean Louis were excited by the project.

Aubouin composed "Le Birthday Diet Menu by Gabriel" for four, with menus that included calorie counts and described the preparation of each dish. He made the challenge even tougher on himself by providing a menu that was low salt, low cholesterol and low fat, while also limiting the carbohydrates.

Six filling courses totaled about 600 calories and less than 700 milligrams of sodium. They contained no salt, sugar, white flour or egg yolks, and the only fish used were those low in sodium; dover sole, said Aubouin, was lowest in sodium of all fish.

Dinner started with a consomm,e of strong vegetable stock with nearly raw julienned winter vegetables; the crunch almost but not quite made up for the lack of salt. Next came boneless frog legs, well seasoned and poached, afloat in a basil sauce with a slightly sweet apple taste. Around the rim were slices of fresh black truffle.

The next course was a terrine of vegetables. Pur,ees of cauliflower, red cabbage, tomatoes and zucchini were arranged in broad stripes, separated by layers of whole- grain pasta and garnished with raw asparagus spears and a red vegetable fleur de lis, and topped with La Brasserie's own no-fat dressing (mustard, raspberry vinegar, herbs).

For the fish course, dover sole fillets had been folded in half and grilled so that they were still moist even though they were quite thin. And they were arranged on a pale gold sauce that was a dead ringer for a cream sauce. Instead, though, it was pur,eed fresh corn, lightly seasoned with curry so that it added a haunting aroma but did not eclipse the flavor of the fish. It was glorious eating. The meat course was sensational from its presentation to its final bite. A saddle of veal had been cut from the bone to allow fresh herbs to be inserted between bone and meat, then yogurt had been rubbed over the meat. It was browned in the oven, then covered to braise with vegetables, including tomatoes and bermuda onions. Presented on a silver tray, it had been sliced and reassembled, the bone gloved in a paper frill. The meat was faintly pink, permeated with enough flavor that it needed not even salt, and rendered so tender in the process that it needed no knife. Alongside was a dark, ruddy sauce made from a pur,ee of the vegetables and pan juices, but the veal hardly even needed that. It was garnished with braised endive and baby carrots barely cooked, with their stems intact.

Aubouin was dissatisfied with the dessert, a raspberry souffl,e made with just egg whites, raspberries and a touch of apple juice concentrate for sweetness. He had tested and retested it, and it puffed nicely (and looked pretty with mint leaves framing a raspberry on top), but without sugar the souffl,e lacked the body to hold its puff, and the juice made it a bit damp. He intended to work it out yet.

It was a dinner we would gladly consign to birthday after birthday. And at $150 for the four of us, after tax and tip, it was an outstanding value for such truffled glory. ean Louis Palladin called to inquire how many calories his dinner should include, and submitted four menus, listing every ingredient and its calorie count, from which we were to choose one.

Our diet dinner was concocted largely from dishes that routinely appear on the menu, and the calories for four courses totaled 543 per person by Jean Louis' calculations, an extra 60 per person by my calculations. (Jean Louis figured light cream at one calorie a gram; in my books it is two calories a gram.) Portions seemed enormous, and we could not begin to finish the meal, but the point to focus on here is culinary quality.

Green asparagus soup with sea scallops was nearly a stew, a thick, pale green bowl afloat with slices of meltingly soft scallops and edged with crisp spears of cooked asparagus. At first the soup tasted so mellow it bordered on bland, but it wore well, improved with each spoonful.

The second course was the highlight: lobster cooked superbly (which means just barely), sweetly full of flavor and prettily reconstructed on the plate without its shell. In this case it was sauced with beets: the sweetness of the lobster and the beets complemented each other, the coral lobster looked smashing against the creamy pink beet sauce, and tiny rosettes of beet pur,ee were horseradish- sharp to add a contrast to the richness.

Calf's liver came next, this one a thick cut, steamed just pink and topped with julienned artichoke and onions. In this case it was the liver that was rich, the sauce light, in all a soft and subtle dish.

For dessert, a plateful of raspberries, all carefully arranged cap up and drizzled with lightly sugared lime juice. Then coffee, for Jean Louis is one of the few restaurants that brews decaffeinated. And a check for $45 a person plus $3 for the coffee, then tax and tip to bring it all closer to $60 each.

It was a diet dinner of culinary glory, served by an enthusiastic staff.