Five minutes after the Rev. Andrew H. Williams Jr. entered a new-style downtown cafeteria he was feasting on chunks of lean white turkey nestled on a bed of lettuce laced with low-calorie salad dressing, a canteloupe salad and iced tea. The cost: less than $4.

"I'm a diabetic . . . and eating downtown here, you usually can't find the kind of food you need to watch your weight," said Williams, an office layout specialist at the nearby Small Business Administration and copastor of a suburban Maryland church. "I watch as well as pray," he quipped.

Williams and thousands of fellow downtown office workers now find it easier to avoid fatty fried foods in favor of quiches, yogurt and a plethora of salads because of a new breed of downtown eatery that has come with the rash of office development in the last 15 years.

Almost completely gone from downtown are the drugstore soda fountain with plastic-topped stools and Formica counters and cheap cafeterias serving hot dogs, hamburgers and half-smokes.

Among their replacements are a growing number of lunch chains led by Lunch Box, Sandwich Chef and Yummy Yogurt that offer a middle ground between the brevity and fattiness of fast food fare and the high prices and variety at expense account spots.

The newcomers, with a total of 26 outlets, most in downtown, are generally marked by butcher block tables, hanging plants and piped-in music. They have an inexpensive but greatly varied bill of fare that leans heavily to nutritious fused with cafeteria quickness.

Sandwich Chef is a national chain. Lunch Box and Yummy Yogurt are locally owned.

Why the switch?

"More and more operations are tending to upscale their restaurants to attract the graying baby boom generation that grew up in fast food restaurants but is always looking for something different," said Dorothy Dee, a spokeswoman for the National Restaurant Association, ". . . and you've got your decor: People like nice surroundings."

Sheldon Fischer, founder and owner of Yummy Yogurt, said, "For the drugstore scene, the food was a sideline. They were not known for top quality food. It was a place to go and wait for your prescription or something."

George Liapis, who established the Lunch Box chain with his brother, added, "The atmosphere has a lot to do with it. When you go to a drugstore counter and look over your shoulder and see a pharmacist or Scott tissue being sold, it just doesn't seem right."

These eateries that emphasize lean and green foods also arrived at a time when downtown office workers -- from secretaries to young lawyers and account executives -- were becoming more weight- and health-conscious.

Phil Klingelhofer, 28, a consumer lending officer for Riggs Bank, munching on a roast beef dinner for $3.92, said, "I really think they have a fantastic deal on the hot roast beef dinner." Cutting thin strips of beef beside mounds of rice and green beans, he added, "And since I'm single and I don't like to cook, I try to get a balanced meal at lunchtime instead of just a sandwich."

While the chains generally look like single-portion grocery stores with shelves of prepared salads and deli sandwiches, sodas, juices and bottled water, each one has at least one distinguishing characteristic.

Yummy Yogurt has more than 10 varieties of toppings for its frozen yogurt. Sandwich Chef has a salad bar. Lunch Box has Greek and Mexican food.

Lunch is their main business, but all three of the chains also serve breakfast beginning at 7 a.m. They are closed in the evening and on weekends, thus tracking the working hours of most of their customers.

Liapis, 37, and his brother, Stratton, 38, who opened the first of the nine Lunch Box outlets in 1971, grew up in the restaurant business.

"There was an absolute market for our type of operation," George Liapis said. "The restaurant-goer was not the same as 10 or 20 years ago. People began to travel, and as they became more educated, so did their tastes."

Sheldon Fischer, 54, who owns the Yummy Yogurt chain with his wife Ann and their son David, 31, said he had his first taste of frozen yogurt in 1976 in a Florida airport.

"I came back to D.C. and went to all of the manufacturers of frozen yogurt and tried to get them to sweeten it and make it more like ice cream," Fischer said.

He opened his first Yummy Yogurt shop that same year. Back then, Fischer said he sold only the frozen yogurt. Now his "Yummy Yogurt Feastery" offers sandwiches, quiche, salads, homemade soups, casseroles, baked goods, ice cream and at some outlets, pizza, fried chicken and barbecued ribs.

"It's tough to make it 100 percent on just yogurt," Fischer said. "Ninety percent of our business is food. Five percent of our business is soup. Salads and sandwiches are the bulk of our sales."

Sandwich Chef Inc., which has restaurants in eight cities throughout the country, started in 1967 and came to the District four years ago. It started out selling deli sandwiches before they were considered healthy food.

"We sort of fell into nutrition," said Alan Kaufman, president and chairman of the board of Sandwich Chef Inc., which is headquartered in Birmingham. "We didn't lead the way -- it came to us. We added the salad bar, baked potato and frozen yogurt. Nobody had heard of these six or seven years ago."

LuAnn Padron, 31, a law clerk with the Commodity Futures Trading Commission located at 20th and L streets NW, is a Yummy Yogurt regular because of its light menu.

"I've got a Mickey Mouse bathing suit I'm trying to get into," Padron confessed as she polished off a 98 percent-fat-free chocolate yogurt with granola topping. "I can get into the suit now," Padron said, "but it would look better if I lost seven more pounds."