Women have another reason to hit the gym, while men may have another reason not to.

The Journal of Applied Psychology found that women who are 25 lbs. below average weight take home an additional $15,572 each year.

On the other hand, men who are 25 lbs. below average weight take home $8,437 less each year.

We knew gender expectations were unfair, but this shocked even the researchers:

"Perhaps the most startling finding of this investigation is that men and women experience opposite incentives regarding weight in the very thin to average weight range. Whereas women are punished for any weight gain, very thin women receive the most severe punishment for their first few pounds of weight gain. This finding is consistent with research showing that the media’s consistent depiction of an unrealistically thin female ideal leads people to see this ideal as normative, expected, and central to female attractiveness."

Workers who fit the ideal have a clear advantage in the workplace, because "employees are more able to influence others and get things accomplished when they conform to the media’s ideal body form."

While overweight men earned more, the researchers speculated that muscular men did even better. Hitting the gym might be a good idea after all:

"Studies have demonstrated that people assign positive personality traits to drawings or photographs of mesomorphic (muscular) men and mostly negative traits to nonmesomorphic men. For example traits ascribed to mesomorphic men were very positive (i.e., best friend, has lots of friends, polite, happy, helps others, brave, healthy, smart, and neat). By contrast ... ectomorphic (slender) men were described with a different set of negative traits (i.e., nervous, sneaky, afraid, sad, weak, and sick)."

Timothy Judge from the University of Florida and Daniel Cable from the London Business School looked at the relationship between weight and income by evaluating a cross-section of American workers. They began by looking at 12,686 participants from a BLS study in 1979.

To understand how weight affects salary, Judge and Cable considered several variables, including gender, education, industry, hours worked, race, height and age -- both which have a strong connection to earnings -- and marital status ("a relatively consistent finding is that married individuals achieve higher levels of objective success than unmarried individuals").

Altogether it's more proof of what we already know: attractive people are rewarded in the workplace.