Obese women who are highly educated earn about 30 percent less — a difference of at least $5,000 a year — than normal-weight or even plump women, the study found. When analyzed by occupation, women with white-collar jobs earned less if they were obese.

Obesity had little or no effect on pay if women were poorly educated, manual workers or self-employed — and no statistically significant effect on men's pay, the study found.

"This suggests that, socio-economically, obesity is not as stigmatizing for men as it is for women," concluded the University of Helsinki researchers.

They couldn't explain why, or why there was a bigger effect on some women, except to say the pressure on women to be thin may be strongest among higher socio-economic classes.

The researchers combed national registries that track Finns' education, occupation and income to choose 2,314 men and 2,068 women for the study. Participants had to be employed in 1993, with no leaves for illness, thus attempting to rule out obesity-caused disease as a reason for lower income.

One limitation: Participants reported their own weight.

The study was published in the American Journal of Public Health.

Source: Yahoo News: Associated Press.