It's accepted wisdom that most people who lose weight through dieting will gain it back. Salads and exercise will give way to pizzas and television - and all the weight they tried so hard to lose.
Must that be so? Researchers collaborating in the largest study yet of weight-loss maintenance say the news isn't quite that grim. But they concede it could be years before anyone finds a dependable way to keep weight off.
The topic looms especially large in light of an obesity epidemic linked to rising rates of diabetes. The problem could grow worse as an aging population finds it more difficult to keep weight off and to resist the temptations of processed foods and ever-better TVs.
In a test of three regimens, dieters in the group that fared the best regained half of the weight they had initially lost. After initially losing an average of 18.7 pounds over six months of diet and exercise, the dieters regained an average of 9 pounds over the next 2 1/2 years.
The dieters regained the weight despite frequent contact with a personal counselor who coached them through the difficulties. To put the result in perspective, these dieters regained only 3 pounds less than those who fared the worst - people who were essentially left to manage on their own.
"One of my colleagues likes to say that weight maintenance is not for the faint of heart," said Dr. Lawrence J. Appel, a professor of medicine at the Johns Hopkins School of Medicine who co-chaired the nationwide trial. "This is nasty business."
Appel and others involved in the study say the results, published this week in the Journal of the American Medical Association, contain hopeful news as well: that keeping weight off is possible, despite the pull of old habits and societal temptations.
"Contrary to popular belief, people can lose weight and keep it off," said Appel, noting that 70 percent of people in the study maintained some degree of weight loss. "The problem is, we don't know the best way."
These are tough times for dieters. Despite the constant eruption of fad diets, evidence has mounted that shedding pounds is easy while keeping them off is hard. Last year, researchers at the University of California, Los Angeles who examined 31 weight-loss studies found that one-third to two-thirds of dieters regained more weight than they initially lost.
"It's just plain difficult to modify your diet and turn away from the pleasures of eating," Michael Goran, an obesity researcher at UCLA, told the Associated Press last year.
But the new study, headquartered at Duke University, was one of the few and the largest to test methods of keeping weight off.
Researchers enrolled 1,700 overweight or obese adults with high blood pressure or elevated cholesterol who then attended 20 weekly group sessions. There, they were taught to eat a balanced diet, keep track of their calories and weight, and engage in brisk walking or other exercise.
After six months, about 1,000 who achieved significant weight loss - an average of 18.7 pounds - were randomly assigned to one of three weight-loss maintenance groups.
In the personal contact group, volunteers spoke monthly with a counselor about their calorie intake, exercise habits, successes and struggles. Nine times a year, dieters and their counselors talked by phone for at least 15 minutes. Three times a year, dieters had face-to-face meetings with counselors that lasted about an hour.
In a second group, volunteers logged onto a Web site where they kept food diaries and tracked their weight and exercise levels. They could also discuss their successes and struggles with other dieters on an online bulletin board. E-mails and phone calls went out to people who didn't log on weekly.
A third group received printed information about diet and lifestyle at the beginning of the study. But aside from meeting with a counselor in the middle of the study, the dieters were left to manage on their own.
The results underscore the odds facing people aiming to maintain a desirable weight. The personal contact group regained an average of 9 pounds, the Web-based group an average of 11 1/2 pounds and the self-directed group about 12 pounds.
Researchers had hoped to see better results from the Web-based strategy because it's cheap and potentially available to millions of people. With nearly two-thirds of adult Americans overweight or obese, personal counseling is simply impractical.
"The magnitude of the epidemic of obesity is too big, and there are not enough weight counselors in the world to maintain these interventions," Appel said.
Evolution may partly explain why people find it easier to shed pounds than to keep them off.
"We're kind of hard-wired to avoid starvation," said Dr. Laura P. Svetkey, a Duke hypertension expert who directed the study. "During the early stages of human development, that was the risk. So, when you lose that weight, the hormones that stimulate hunger increase."
People must also weather a barrage of social pressures that tempt them to "eat badly and underexercise," Svetkey said.
People go to bookstores and find an attached coffee shop offering high-calorie scones and pastries, she said. They dine at restaurants that serve "gigantic portions, much more than you need to sustain weight."
What's more, modern life is almost rigged to keep people sedentary.
"You don't even have to turn a doorknob in most buildings or roll down a window in your car," she said. "These are very little things, but if you put them all together, you really have to decide to exercise."
Ann Power, a study volunteer in the personal contact group, had already worked exercise into her life. For years, she had been in the habit of walking four or five miles around her Catonsville neighborhood. Once in the program, she increased her regimen from five days a week to seven.
Power, 65, weighed 175 pounds when she enrolled in the study, and she managed to lose 12 pounds during the initial phase of dieting. She not only managed to keep the weight off, but she continued to lose weight after the study ended.
"The biggest thing they tell you is to keep records of what you eat," said Power, 65, a retired Realtor. "If you write it down, you know that you ate 3 ounces, not 8 ounces, of roast beef, and you keep track of how many fruits and vegetables you ate."
She also credited her Hopkins-based counselor with helping her to stay focused and positive, even when a personal illness made her doubt whether she could stay in the program.
Power's success might be unusual, but researchers with the study said they would like to combat the notion that dieting is futile and backsliding spells defeat. Svetkey, for instance, said a pound or two of weight loss can lead to a one-point drop in blood pressure.
"If you lose 10 pounds, your blood pressure might come down 10 points," she said. "If you lose a couple pounds of weight, there's also a 16 percent reduction in the chance of getting diabetes. That's a little bit of weight loss, a lot of benefit."
Now the researchers are trying to determine which elements of the programs are most important to maintaining weight loss. Perhaps, they say, the essential ones can be incorporated into a program that's less expensive and labor-intensive than personal counseling.
"I'm sure there will be nothing that's one size fits all," Svetkey said. "We need to develop a toolbox of maintenance strategies that work for different people and find a way to make it affordable."
Struggling to keep weight off once you've lost it? Here are some tips from Drs. Lawrence J. Appel and Laura P. Svetkey, weight-loss experts from the Johns Hopkins and Duke medical centers, respectively.
Weigh yourself frequently - not necessarily every day, but frequently enough to catch signs of improvement or backsliding.
Record calorie intake, a strategy that can help to remind you that fruit juice can have as many calories as sodas.
Exercise regularly and keep track.
"Avoid mindless eating, the M&M;'S and candies or whatever foods seem to be readily available," Appel said.
Set realistic goals and keep frequent records that show whether or not they are being met.
"Think about your motivation," Svetkey said. "What is it that made you want to lose weight in the first place and keep it off?"