Today is the first day of a new diet that involves never eating another cookie again. Sound like your New Year's resolution? If so, weight control experts say, it's probably doomed to fail.

Seasonal dieters are much less successful at maintaining weight loss than those who follow healthful diets all year round, said Virginia Inglese, president of Total Health Concepts Inc., a nutrition, exercise and stress management center in Falls Church. Inglese said that participation in her aerobics classes usually doubles during January and February, then drops off, surging again before bathing-suit season.

There are lessons to be learned from people who don't resolve to lose weight every January 1. Here are some of the techniques employed by the estimated 30 percent of those who embark on diets and manage to keep weight off for at least a year.

They set realistic goals. To shun cookies forever or vow to exercise every day is "self-defeating behavior," according to Fran Taylor, a Bethesda software consultant who lost 25 pounds and has kept it off for more than a year. What ends up happening is that "you beat yourself up for not doing it," she said. A feeling of failure ensues and so do previous eating habits.

They eat regularly, and don't skip meals. As many people unfortunately do, Art Winschel, a local financial planner, ate a lopsided diet: he'd skip breakfast and have a huge meal at night. Now, Winschel, who lost about 35 pounds and has maintained it for more than a year, typically eats cereal with fruit and skim milk for breakfast; a bagel or toast for a mid-morning snack; a turkey sandwich for lunch instead of his previous fast-food routine; low-fat yogurt as an afternoon snack, and a light dinner. He said he feels like he's eating more and doesn't feel deprived.

They exercise regularly but not excessively. When people are told they have to exercise to lose weight and maintain it, sometimes "they panic," said Paul Flaherty, a Vienna consultant who has weighed 75 pounds less for almost a year. They think they have to stock up on all kinds of new sports equipment, when if they just walked or took an exercise class a few times a week, they'd be fine, he said.

They lose it slowly and don't rely on packaged powders or other special foods. Ed Gerry of McLean, who works at the Department of Defense, said he tried a lot of fad diets but has realized that the "sensible approach" -- simply exercising and choosing nutritious food -- is the most effective. With Inglese's help, he slowly lost 30 pounds -- and kept it off for a year, longer than with any of the other diets he tried. Recently he broke one of his knees in a skiing accident, throwing a wrench in his exercise routine; he regained some of the weight, but he's slowly taking it off again.

They find the fatty foods they once savored unappealing -- too rich or overly greasy. "I enjoy eating more now than ever. I'm eating better quality food, and it tastes better. The other stuff is junk," said Herb Brubaker, a University of Maryland English composition teacher who has kept off 90 pounds for more than a year.

They incorporate planned splurges into their regimen. Brubaker loves cheesecake. So he'll indulge in a "big fat piece" once every two months. But that's it. He won't do it again for another eight weeks, and he doesn't feel guilty about it. "I consider it part of the routine," he said.

Similarly, Winschel said, he follows a healthful eating pattern about "80 percent of the time." Lobster, he said, just isn't the same with margarine.

They don't think they are "on a diet." Winschel said his new eating pattern is "part of my life. It's no big deal. You get beyond the stage where you'd kill for a french fry."

They realize it takes effort, willpower and concentration to change lifelong eating patterns but find the rewards to be great. Said Brubaker, "I could never go back to the old ways of eating sloppily and poorly. I'm just having too much fun."

Eating Right appears on alternate Tuesdays.