Nearly one-third of overweight Americans don't think they are too heavy, and men - far more so than women - refuse to acknowledge that flabby form filling the mirror, a national survey shows.

The annual survey of various health-promoting practices found that 64 percent of American adults are overweight. Of those, 31 percent feel they are "at about the right weight."At the same time, 14 percent of Americans are underweight, of whom 77 percent think they are at about the right weight, according to the survey released Thursday by Louis Harris and Associates for Prevention magazine.

Overall, Americans scored 66.2 out of 100 in the November survey of their health practices, the same as a year earlier. But that score is up from 61.5 percent in 1983, the year of the first survey.

The survey measures practices such as smoking, alcohol and drug use, exercise and weight control, diet and nutrition, control of stress, frequency of medical exams and safety precautions at home and in the car.

The survey found that health behavior "has improved significantly since 1983, with greater numbers of individuals actively watching key elements of their diet such as their cholesterol level," a summary said.

But it called the lack of overall progress in the past year surprising and said the nation needs to foster "a climate that encourages habits such as healthy eating, regular exercise or daily stress control."

The most significant setback detected in the surveys was in controlling weight, the magazine said. The proportion of Americans who are overweight has risen six percentage points since 1983.

It said 36 percent of Americans are at least 10 percent over the recommended weight for their height, sex and build, based on widely used life insurance company tables.

"Overweight women are far more likely to see the reality of their physical condition than overweight men," the report said. "Men are twice as likely as women to feel `at about the right weight' when they are in reality overweight."

It added that "the first step toward overcoming a weight problem is often simply recognizing that a problem exists."

Forty-six percent of those with a weight problem said they had tried to lose weight during the past month. But among those who acknowledged they had a problem, 56 percent had tried to shed weight.