Considering the high cost of lunch these days, it's often better to do without. And many Washingtonains are doing without while keeping their bodies trim and their minds challenged.

Ironically, the people engaging in the most rigorous activities are the ones protesting the loudest that they're not athletic.

Hayward Coe, 35, an accountant at the Department of Energy and the only man in a lunch-hour aerobic dancing class of 10 women says, "I hated physical education in high school, and I don't like regular kinds of exercise. I do like new and different things to learn and to dance. These exercises can be used in disco dancing, too."

Janet Richardson, 34, a personnel counselor at Time-Life Books in Alexandria, says that, like many women, she was conditioned not to participate in strenuous sports. "I went to school in Europe and I wasn't allowed to play contact sports. I always watched my brother." Now, encouraged by the men at Time-Life, she's part of an 11-person co-ed soccer team that plays at lunch time two or three days a week.

While the most obvious reasons for skipping lunch would seem to be a thin purse and a fat middle, men and women have many other rationales.

David Thaxton, 36, a filmmaker and historian, wanted to use up some exercise energy. He decided to learn Tai Chi Chuan, a classical Chinese dance form taught at the Almega Institue on 18th Street.

Combining calisthenics and control, Tai Chi "channels energy," says Thaxton. "It's not strenuous like weight lifting, but you do work up a sweat. There are 37 positions that take three months to learn, then you repeat the forms automatically. It's like swimming in air: very slow motion. It restores my sanity."

Comfort has little to do with exercise, as summer tennis players and joggers confirm.El-Motez Sonbol, 42, first secretary of the Egyptian Embassy, calls Washington's humidity "beautiful, exactly like Egypt." A former member of the Egyptian Davis Cup team, he plays tennis on summer lunch breaks at the St. Albans courts in Northwest; in the winter, indoors at the Airlington YMCA.

Dennis Flannery, 40, lawyer and jogger, runs from 3 1/2 to 8 miles daily "as a good alternative to work or going out to eat. . . . My mind floats freely. If I've been working on a problem, sometimes I'll have an insight that makes it seem less complicated."

Donald Chaikin, 45, lawyer and former part-owner of the Philadelphia franchise for the World Football League, attends a Bible-study class once a week with 15 others: lawyers, bankers, physicians and accountants. Shmuel Kaplan, a Lubavitch rabbi from Baltimore, comes to Washington Thursdays to teach the class.

Making music during a lunch hour is also possible. Carol Warden, 34, general manager of the Dale Music Company in Silver Spring, says that over the years people have dropped by and asked her if she'll play duets with them. Although she doesn't do that, she says "we do rent instruments and practice studios at lunch. One man comes in twice a week, brings his own music, and practices his cello."

Office reaction to non-conformist behavior like soccer playing, aerobic dancing, Bible study, or weight lifting often depends on the person's status or unbashed enthusiasm.

"I'm the boss here. No one laughs at what I do," says Charles Akre, 36, vice president adn manager of the Alexandria office of Johnston, Lemon and Co., a stock brokerage firm. What he does is work out at the Atrium Penthouse Health Club with 200 rope skips, 110 sit-ups, and 100 bench presses, chin-ups or push-ups daily. No laughing matter.

When Jennifer Porter, 23, a mail clerk at the National Food Processors Association, began slimnastics classes at the YMCA on 17th Street, her friend, secretary Emma Pryor, 26, joined her the next day. "Everybody wanted to join when they heard what I was doing," says Porter.

And then there are people like TV newscaster Susan King, 31: "My alternative to lunch is - working." Alternatives to lunch: YWCAs and YMCAs - Noontime classes include swimming, aerobic dancing, "Wise weight and a healthy back," belly dancing and yoga.

Health clubs - They have lunch classes, too, but you may have to pay a higher membership to join.

Study groups - They're hard to find. Word-of-mouth is the method.

Take the Metro and sample the museums. They often offer lunch-hour films and lectures. CAPTION: Picture, Left, David Thaxton and Maggie Leigh doing T'ai Chi during lunch hour. Photo by Harry Naltchayan - The Washington Post.