For example, the proportion of women who did not feel sexually attractive fell from 68 percent before they began a weight loss program to 26 percent a year later.

There were similar decreases in the percentages of women who didn't want to be seen undressed, had little sexual desire, avoided sexual encounters, had difficulty with sexual performance or didn't enjoy sex.

"There are a lot more appearance-related pressures on women," said lead researcher Martin Binks of the Duke Diet and Fitness Center in Durham, N.C.

While the results aren't a surprise, the study nevertheless is valuable, said clinical health psychologist Lyssa Menard of Northwestern Memorial Hospital's Wellness Center. "Sometimes we forget to study the obvious."

An earlier study found that 65 percent of obese people seeking treatment at the Duke center had impaired sex lives, compared to 5 percent of normal weight people.

Participants lost an average of 17.5 percent of their body weight after one year. That translates to, for example, a 240-pound woman losing 42 pounds or a 280-pound man losing 49 pounds.

This is cache, read story here