From CNN Medical Corrrespondent Elizabeth Cohen

ATLANTA (CNN) -- The National Institutes of Health has some advice for people who are no more than 30 pounds overweight: quit trying to lose weight.

The obesity experts say that being 30 pounds overweight isn't all that dangerous, and studies show most people gain it back anyway.

The NIH this week published information relating to the strict set of guidelines it set out in June for determining who is considered overweight. The guidelines, which were seen as controversial,are based on theBody Mass Index (BMI), a height-to-weight formula that ignores whether the weight is from fat or muscle. It also ignores whether someone has a large or small frame. The weights are the same for men and women.

The new NIH guidelines mark a turning point in the way doctors think about weight loss, Dr. Xavier Pi-Sunyer , chairman of the NIH obesity panel and director of endocrinology at St. Luke's-Roosevelt Hospital in New York, said in an interview with CNN.

According to the NIH report, a person who is 5 feet 4 inches tall and weighs 174 pounds is 30 pounds overweight. A person who is 5 feet 10 inches tall and weighs 209 pounds is 30 pounds overweight.

The experts urged people less than 30 pounds overweight to prevent any further weight gain; the average American gains between half a pound and a pound per year.

There are some exceptions to the new rule. If you're less than 30 pounds overweight, you should actively try to lose weight if you have two or more risk factors, including heart disease, diabetes, high blood pressure, high cholesterol, and fat that is all gathered around the waist.

When doctors refer to fat gathered at the waist they are referring to a condition in a minority of people who have fat just at their waist and not in other areas of their body.

According to the new guidelines, people more than 30 pounds overweight should try to lose a half a pound to a pound per week, and then maintain that weight loss for six months before trying to lose more weight.

People who are "obese plus" -- those who weigh about 350 pounds or more -- should talk to their doctors about more drastic approaches to weight loss, including surgery.

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