Americans, addicted to fast food but obsessed with looking trim, can now order instant gratification -- hold the guilt. A new restaurant chain, D'Lites of America Inc., is offering reduced-calorie fast food.

Doug Sheley sensed opportunity in the cravings of the diet-conscious when he owned a chain of 18 Wendy's restaurants. "Customers kept asking me things like, 'How many milligrams of sodium are there in one of your hamburgers? How many calories in a shake?' " he explains. "It gave me the idea to combine different facets of eating."

In 1981, Sheley sold his franchises and opened the first D'Lites fast-food outlet in Atlanta, eventually adding three more in the same city. The D'Lites menu offers the familiar burger-and-fries fare that about 13 million Americans order every day. But a typical D'Lites meal has some 500 fewer calories and less saturated fat, carbohydrates, and cholesterol.

The burgers are made with lean ground beef, Sheley says, containing 20% fat, compared with up to 30% fat in a normal hamburger. Buns are made from multigrain or light white flour, containing 25% fewer calories than ordinary white flour buns. The selection also includes such items as chicken and fish sandwiches, vegetarian sandwiches served in whole wheat pocket bread, an all-natural salad bar, sugar-free colas, light beer and wine, and frozen dairy desserts with 40% fewer calories and 75% less cholesterol than ice cream.

So far, Sheley seems to have found a recipe for success in the highly competitive $41-billion-a-year market for fast food. Other chains, such as Burger King, Arby's, and Wendy's, have begun to respond to the trend toward healthier fast food by offering such alternatives as salad bars and vegetables in pocket bread. But Sheley's restaurants are in the vanguard. His four Atlanta outlets average sales of almost $1.1 million each, compared with the national average of $300,000 per fast-food outlet. Since April 1983, Sheley has sold franchises for 521 more restaurants at about $25,000 each, in cities throughout the country. Revenues for the entire D'Lites franchise are growing by about 21% a year, Sheley says, and he hopes to expand the chain to at least 1,000 restaurants in the next decade.

But Sheley says he is not taking on the big chains directly. Instead, he is trying to attract a new clientele to the fast-food market: "We're drawing upscale groups of people who would never dream of walking into a McDonald's."