Researchers are putting a tag on obesity. Doctors have known that medical bills are higher for the obese, but a report from George Washington University finds that's only a portion of the real-life costs.

The researchers added in factors such as employee sick days, lost productivity, even the need for extra gasoline-- and found the annual cost of being obese is $4,879 for a woman and $2,646 for a man.

That's far more than the cost of being merely overweight -- $524 for women and $434 for men.

The study's co-author Christine Ferguson says the difference found between the sexes suggests that larger women earn less than skinnier women, while wages don't differ when men pack on the pounds.

Two-thirds of Americans are either overweight or obese, and childhood obesity has tripled in the past three decades.