Is aerobic exercise (intensive exercise that gradually elevates the heart rate, keeps it there for a time, then returns it to normal) here to stay?

One may notice that sheer numbers have fallen off at aerobic dance classes. But since aerobic exercise also includes such stamina-builders as jogging, fast walking, swimming and cycling, there are an estimated 22 million people in the country who participate, according to IDEA, the International Dance-Exercise Association.True enough, the first wave of beauty-conscious people who saw aerobic dance primarily as a quick road to body shapeliness has gone by. But those who remain are inclined to be into aerobics for the long haul, espousing a regimen that can increase fitness and endurance, and promote a healthy heart and lungs. Without doubt, aerobics has had a great positive effect upon the country's fitness in the past 15 years.

This more serious emphasis was apparent at the recent Utah conference of IDEA, "the only organization dedicated solely to meeting the needs of fitness instructors and business owners in aerobics, and all forms of exercise to music," according to its brochure. Since its organization by Kathie and Peter Davis in San Diego in 1982, IDEA has attracted more than 14,000 members across all 50 United States and in 45 countries.

IDEA now publishes nine issues a year of its magazine, Dance Exercise Today. And the IDEA Foundation is working toward industrywide certification, testing, research and consumer education. In May 1986, IDEA Foundation conducted the first industry standardized certification examination based on training guidelines.

The test is administered by the Education Testing Service, which also gives the SAT college entrance exams. More than 4,000 instructors took the exam in two offerings in 1986, and it is now given quarterly across the country.

About 75 Utah aerobics instructors gathered this month for an IDEA workshop at the Red Lion Inn. Among presenters at the convention was Ronda Gates, whose LifeStyles is a fitness, education and health promotion firm with headquarters in Lake Oswego, Ore. (P.O. Box 1843, OR 97035).

A former associate director of Covert Bailey Seminars, she was instrumental in developing the Fit and Fat Systems. She works closely with IDEA as northwestern regional representative, has written several books, and delivers exercise, nutrition, personal growth and body fat lectures and workshops nationally.

Gates holds a master's degree in pharmacy, but feels that "aerobics are more fun." As she taught aerobic dance for eight years at her studio in Portland, she became increasingly aware that exercise alone is not enough. One must learn about nutrition, which plays an all-important role in well-being. She decided her best contribution would be to work in depth with teachers on general health promotion.

Nor does one go far before running into the psychological complexities of how food, mood and behaviour are closely intertwined. "Many people use food to avoid coming to grips with life and finding a balance," she said.

Conflicts on the one hand, and boredom, deja vu on the other, are inevitable as life unfolds, she said. "When people are young, they go along in the hope that everything will work out OK, that they will live without adversity. But as they get into long-term life relationships with long stretches of monotony, the time often comes when they think, `There has to be more than this.'

"It is then that most people go in search of self-esteem, which is the underlying necessity for everyone's success; and how you look is basic to it. An awful lot of girls first took up aerobics to improve their body image, to `fix' their bodies. They have remained for the sense of well-being and fitness they experience.

"But many people, especially women, are terribly demanding of themselves. It was interesting to me that when I asked a roomful of aerobics instructors, most of them very attractive women, how many were happy with the way their bodies look, hardly anyone raised her hand. I think I was actually the only one who did so!"

Gates sees getting in touch with and accepting your own physical self as a great help toward resolving conflicts, perceiving your own and others' gifts, really seeing each other, being more accepting and less judgmental. "When you really know and accept yourself, you are ready to do something for others," she said.

Speaking before the instructors later, she zeroed in on fat as probably the single most destructive element in the American diet, and "fatness as the nation's No. 1 killer."

Some tips from Gates on how to improve low-fat food selection should help the person who seeks to permanently subtract a few unwanted pounds, preferably without too much pain and deprivation:

***There are 4 calories in a gram of protein or carbohydrate, 9 calories in a gram of fat; obviously, you can eat more carbohydrates and protein while losing weight faster and/or maintaining better. But most people eat about 50 percent of their food in fat, while the surgeon general's recommended daily fat intake is 30 percent.

***Don't expect to lose more than 2 pounds of fat a week; greater losses are just water. A low fat, high fiber, balanced and varied diet of 1,200 to 1,500 calories minimum will work best for livable, lifelong weight control. Develop a diet that lets you eat as much as you can of acceptable foods. Fiber moves through the system most quickly and efficiently.

***A pound of fat is 3,500 calories, so if you eliminate 250 calories of fat a day from your diet and burn 250 calories in additional exercise, you can get rid of 1 pound of fat a week.

***Since much fat is concealed in prepared foods, learn to read grocery store labels and quickly evaluate fat content. Labels can be very deceptive, with ambiguous terms like "95 percent fat free." By law, a "reduced calorie" label means at least one-third fewer calories than the regular product.

***Light sour cream has half the calories of regular sour cream. Butter buds are a great-tasting butter substitute, with scarcely any calories, and sprays for frying, with no calories, are apparently checking out for safety over the long run.

***General dietary considerations: Notice that sugary cereals are lined up on the grocery shelves at child eye level. Oats are the best grain for decreasing cholesterol - and the less finely processed, the better. Calcium is an un- necessary additive in cereal. You should get it with milk, especially when fortified with Vitamin D, which helps to utilize it.

***Sea salt is no better than any other salt, and all salt is to be avoided. Buy tuna packed in water rather than oil. Crackers are 31-37 percent fat. A 21/2-pound chicken eaten with the skin contains 2,400 calories; cooked in the skin but served without, 1,600; and cooked without skin, 800 calories.

***Some recipe suggestions: Non-fat yogurt has many delicious applications, in dressings and toppings. Angel cake, a non-fat dessert, is good served under chocolate pudding, prepared with skimmed milk.

***Try making Snow's clam chowder with skim milk and an extra can of clams. To avoid fat and salt, don't eat nacho chips; instead cut up tortillas, heat in the microwave oven and serve with salsa mixed with beans. Mustard is another condiment without calories. A potato is high in carbohydrates, no fat, so a potato bar with lo-cal toppings makes a good party entree.

***For a holiday present, rather than a basket of cookies and candies, Gates demonstrated a gift basket that contained fresh flowers, books and magazines, including "Cooking Light," a calendar, bean soup mix, popcorn with Molly McButter ("a wonderful butter substitute," she said) and a fat-skimming gravy pitcher with the spout at the bottom.

Or there might be a copy of her own "Low Fat Lifestyle," a book of recipes, health and fitness tips, co-written with Valerie Parker. Since 1983 it's sold 30,000 copies, and is due for a re-print.