It's not what you eat, but how, when, where and why that makes you overweight. That at least is the argument of Dr. Henry Jordan, 40, associate professor of psychiatry at the University of Pennsylvania School of Medicine and co-author of the recently published Eating Is Okay! (Rawson Assoc, $7.95). A graduate of Harvard with an M.D. from Penn, Jordan set up the Behavioral Weight Control Program at the university hospital with his co-author, psychologist Dr. Leonard Levitz. More recently, they established the Institute for Behavioral Education, an independent study center for obesity, where more than 200 overweight adults and children are treated a year. Dr. Jordan lives in an 18th-century farmhouse outside Philadelphia with second wife Barbara, 31, and three children, aged 5 to 17. He still tries to keep within 10 pounds of his weight as a member of the Harvard crew (180 pounds). Recently he talked to Barbara Kevles for PEOPLE about correcting often unconscious eating patterns.

Is it physically dangerous to be obese?

Yes. Statistically, obese people live shorter lives. It's also thought that obesity contributes to hypertension, diabetes and cardiovascular diseases.

Whom do you consider obese?

Anyone who is 20 percent or more above the ideal weight for their height.

How many Americans are obese? Estimates are from 20 to 50 million.

Why do so many diets fail to achieve a permanent weight loss?

Diets that depend on drugs or fads—like the water diets—count on patients following the dictates of the therapist. But when the patients go off their rigid diets, they often revert to their old ways because they never learned in the first place why they eat the way they do.

What is your approach to reducing?

Our method is based on the age-old prescription for weight loss—limiting calories and increased exercise. But, in addition, we change how a person reacts to those environmental, social and personal influences that originally caused the overeating.

What success have patients had with your method?

In our program 65 percent of our patients lose 20 pounds or more, and 15 percent lose more than 40 pounds. After a year our figures show that 85 percent of those who lost 20 pounds have kept their weight down or lost more. For many programs the success rate after a year is only 5 percent.

What's the first step?

To become aware of your eating habits and what triggers them. We have our patients keep detailed diaries of their eating, not only calorie counts but also the time, length, place, physical position, whom they're with and mood in which they eat.

Then what do you do with these diaries?

We go over them together, looking for good habits as well as bad. Many people have control most of the day, but they may find one period when they get into trouble. Overweight people feel all their eating habits are wrong, and this is not true.

Must a dieter sacrifice favorite foods?

No, whether it's ice cream, candy bars or eclairs. All we ask is that they plan their calories to allow for it, eat it slowly and savor every bite.

How do you teach a patient to cut down on his favorite dessert?

There is no way to curb pleasure from a favorite food. We would rather increase that pleasure. We might ask that person to have his favorite course first—even if it's dessert. He might then pass up less preferred food later because he felt stuffed.

Does any single activity prompt overeating?

Most commonly, eating is paired with simple routine activity. We had one patient who snacked almost continuously while cleaning house and listening to the radio. We discovered she had made a special apron with pockets big enough to hold candy, cookies and even bottles of soda pop. She never had to make a deliberate decision or take another step to eat. Obviously, the first step was to get a new apron without pockets.

Do people overeat out of stress?

Contrary to popular belief, very few patients overeat out of tension, depression or anger. More commonly, people eat too much when they are bored or tired.

How does life tempt overeaters?

People are bombarded nowadays by cues to eat. Then, too, more food is available through easy-to-open snacks, vending machines at work and even the supermarket. We had to teach one patient to recognize the supermarket's subtle enticements, and to shop only after a meal.

Is being overweight typically a woman's problem?

No. A man's eating behavior is equally influenced by his environment, though often his problems occur at work, rather than at home. One man, whose job required him to travel, ate all his meals and endless amounts of junk food at the wheel of his car. We advised him that if he truly wanted to eat he should stop at a restaurant and take time for a satisfying meal.

Does how fast a person eats influence how much he eats?

Yes. Studies from our human feeding laboratory show that if a person of normal weight eats quickly, he will tend to eat more. In one experiment, subjects who rapidly drank a liquid diet from eight-ounce glasses consumed more than when drinking the same diet from two-ounce cups. With the smaller cups the subjects paused more often, drank at a slower rate and consequently consumed fewer calories.

Do people stop eating when they are full?

Not always. In some experiments, we fed people by mouth and by stomach tubes. The results demonstrated that the desire to continue tasting food was stronger than the signals to stop eating that come from a full stomach. People may overeat simply because the food tastes good.

Do patients ever experience setbacks from spontaneous food binges?

Yes. Life is such that no one can control behavior 100 percent of the time. It is important that our patients experience a binge so they learn not to feel guilty or a failure. Guilt is a useless emotion. The danger, of course, is that when patients go on binges they may never return to dieting again. We advise that an uncontrolled episode be analyzed, understood and accepted.

What other hazards lie in wait for the overeater?

Often where the food is stored is important. One patient ate three to four boxes of pretzels a week from a jar on her kitchen counter. One day she put the jar in the pantry. As a result she cut down to one box. There are other things that can be done—freeze leftovers so they are less readily accessible or put snack foods in the rear of the refrigerator.

How can the weight reducer handle the unavoidable social situation?

A person can always plan his or her business lunch menu or at least exert some control. No one is forced to stand next to the hors d'oeuvres table at a party or order dessert. It's important outside the home to make other people help you exert control without giving up your own authority.

What maintains a weight reducer's motivation to lose?

Most often, the single most important factor is a patient's realization that he or she can control the eating that previously was unmanageable.

Do spouses help or hinder weight loss?

Sometimes they will sabotage their mate's efforts so as not to jeopardize the relationship between them.

How can people incorporate more exercise into everyday living?

First make a list of all the labor-saving devices you use in a day—escalators, elevators, electric can openers, cars—and then decide which ones you can do without and when. We had one woman who had not walked to the nearby grocery store for 25 years. Isn't that incredible! The first time she made the trip by foot the neighborhood children asked her if her car was broken. At the office a secretary who switches from a manual to an electric typewriter can gain up to six pounds a year.

How can parents train their children to have good eating habits?

By example. Parents must be careful not to impose their likes and dislikes about food on the child. A child should have the freedom to experiment with food or to refuse it. "Bottoms up!" and "clean plates!" should be left behind with the Great Depression.