Call it diet fatigue, burnout or simply boredom.

That's what Laura Howard, a Lean Plate Club member who has trimmed an impressive 60 pounds during the past 18 months, reports experiencing these days. To drop from 190 to about 130 pounds, she's done all the right things, including working out four times a week, changing her eating habits, even altering the way she thinks about food.

Yet she's now slipping into "bad habit" quicksand.

"Over the past few months," she wrote in an e-mail last week, "I've been finding it harder to stay motivated . . . and am feeling the pounds come back. . . . I'm up to 136, which isn't a lot, I know. But I'm so worried I'm going to be fat again.

"The weird thing is, I don't do anything about it. I will sit around and worry about being fat and gaining the weight back, but I have no ambition to get on the treadmill or go for that bike ride except for once or twice a week. . . . I don't even have a reason like 'I'm too busy.' I just simply don't want to.

"I have hit a wall . . . and can't get seem to get back to the mind-set I was in during my most motivated time. Help me so I don't gain it all back!"

At the University of Pennsylvania's Weight and Eating Disorders Clinic, "about 100 percent of the people we see feel this kind of fatigue," said Leslie Womble, assistant professor of psychiatry. It's so common that Womble warns them about it before it happens so "they won't be surprised."

Most shrug off her alerts -- and a few get annoyed -- until it happens to them. That's because losing weight can feel exciting when reinforcement is strong.

"At first, when you're plugging away, it feels great because everyone is noticing," Womble said. "You start to look great and your clothes size is changing."

But maintaining those hard-fought losses takes just as much effort and comes with less positive feedback because it's simply keeping the status quo.

"Quite honestly," Womble said, "it is hard to keep the weight off."

Most research has focused on how best to shed pounds -- not on how to maintain the loss for the long haul. So these days, "we're trying to develop whole programs to study this very point," said Rena Wing, professor of psychiatry and human behavior at Brown University School of Medicine and co-director of the National Weight Control Registry, a database of more than 3,000 people who have lost at least 30 pounds and maintained the loss for at least three years.

Until scientists can shed more light on the mystery of weight maintenance, here's what experts advise:

Look at the big picture. "Most diets are a 100-yard dash," said John Norcross, professor of psychology at the University of Scranton and author of "Changing for Good" (Avon). "We know that changing lifestyle is a marathon."

Relax -- a little. Womble advises figuring out small ways to loosen up, not quit. So if you've been recording every morsel that passes your lips and can't bear the thought of writing down another entry, then note what you eat every other day. Or just on weekends. Or just after 3 p.m., if nighttime eating is a problem. "That way," Womble said, "you can get a little bit of a break. These are ways that people can step back a little."

Draw a red line. At the University of Pennsylvania clinic, Womble suggests people in maintenance draw a red line either five or 10 pounds above their current weight. If weight rises above the red line, participants immediately reinstate the full spectrum of habits that worked to help them achieve their weight loss goals.

Make it fresh. Boredom often undermines long-term habits. "So try to create variety," Wing said. "If you always walk, this might be a time to try biking. Same thing with diets. If you're in a rut, this may be the time to get out your magazines and find some recipes. Invigorate yourself."

Recruit a buddy. Being accountable to someone else means that it's not so easy to skip a workout. "If you know a friend is waiting to meet you, you're less likely to not go," Womble said. "I do that myself." Another option: consider a session or two with a personal trainer.

Mix things up. Research suggests that doing different types of physical activity helps create muscle "confusion" so that plateaus -- and boredom -- are less likely to occur. So walk a different route to work. Do the weight machines at the gym in a new order. Work out at a different time of day. Get a pedometer to help boost activities like walking and taking the stairs. You get the idea.

Test yourself. Changing behavior takes time. Figure on at least six months -- often far longer -- to make a new habit a permanent lifestyle change, Norcross said. How do you know when you've reached that point? One test, Norcross said, is that you can engage in the behavior at any time or in any situation. So whether you're under stress, celebrating a holiday or visiting a friend, you have confidence that you still stick with your new routine. For Norcross that test is travel. "The last thing I want to do is to haul my butt out to the exercise facility at a hotel," he said. "But I do it."

The second test is if you can overcome the temptation to slip into old habits with nary a thought. "It's when you can see the dessert cart and it's not gnawing at your soul," Norcross said. That's when "a short-term change has become a permanent lifestyle," he said.

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