"I prefer the term `treat' to `cheat,"' said Eitner, of Menlo Park, Calif. "If it gets out of hand, the person shifts gears and deals with it. To me that's a healthy relationship with food; under control, but not overly controlled."

That's also what the American Dietetic Association preaches.

As spokeswoman Cynthia Sass, a registered dietitian in Tampa, Fla., pointed out, "there's a huge difference between an entire day of binging and a little bit of splurging each day."

Sass' group recommends that 80 percent of food consumed be nutrient-rich, and spread over the day. This leaves room for a little treat -- perhaps one piece of high-quality chocolate.

"I had a client the other day who was very good during the week and ate whatever she wanted on weekends," Sass said. "She hadn't lost any weight because she was surpassing the calories cut during the week on Saturdays."

The man who literally wrote the book on cheating is Paul Rivas of Baltimore, author of "The Cheater's Diet." He's worked as an obesity physician for more than a decade and claims success with thousands of patients on controlled cheating plans.

The key is "controlled."

"If they know after one piece of chocolate they'll have to eat a pound," Rivas said, "they can't have it."

Rivas said his plan works because it charges the metabolism.

"The biggest thing on any low-calorie diet is that the metabolism drops," he said. When the body adapts to the reduced amount of calories, weight loss stops. "But this keeps it off balance. You're giving the body more calories one or two days a week. The metabolism has to go up."

Steven G. Aldana disagreed. "The changes in metabolism we see between people, from the highest to the lowest, are mostly due to genetic differences," he said. Calorie intake causes an "insignificant" change.

Aldana is a professor of lifestyle medicine at Brigham Young University in Provo, Utah, and author of the upcoming book "The Stop and Go Fast Food Nutrition Guide," which assigns red, yellow or green ratings to unhealthy, moderate or healthy selections at some 90 chain restaurants.

Other experts are concerned that cheating actually makes dieting seem more onerous, something to be endured.

"Eating every day should be about health, enjoyment and conducive to weight control," said David L. Katz, an associate public health professor at Yale and director of the university's Prevention Research Center.

That's also Linda Roberts' view. "You just can't live on a `diet,"' she said. "I wish we'd just do away with that word."

Roberts is with Abbott Laboratories, an international health-care company with headquarters in suburban Chicago. Abbott recently acquired Body for Life, a popular nutrition and strength-training program that incorporates a cheat day.

"Yes, there is a free day," Roberts said. "But participants can't go out and have 15,000 calories in a day. That defeats the purpose."

Instead, "we try to get them to think of it as a free meal, and limit it to once a week."

June 30, 2006