When Jennifer Portnick wanted to be a Jazzercise franchisee, she says she was denied. The reason: The company had a policy that required exercise instructors to appear fit. Portnick, who weighed 240 pounds, didn't pass.

So she filed a civil complaint under a San Francisco ordinance that bans discrimination based on weight and height. The company changed its policy, and she dropped her complaint.

Portnick's story shows how physical appearance can affect employment. A growing body of research supports what many suspect: In the workplace, an employee's physical appearance is a powerful symbol that has an impact on job success.

"The issue was my image. I never thought I'd be complaining about discrimination," says 41-year-old Portnick, who now is a personal trainer and teaches intermediate aerobics classes for people of all sizes.

Jazzercise officials say they don't believe they discriminated against Portnick.

The new research, as well as high-profile lawsuits alleging appearance-based discrimination, is raising new awareness about how looks can hurt — or help — careers. It also has some organizations such as the International Size Acceptance Association calling for legal protections.

In some cases, they're getting it. Michigan bans discrimination based on height and weight. Santa Cruz, Calif., bans discrimination based on height, weight or physical characteristics. Washington, D.C., outlaws employment discrimination based on personal appearance. In San Francisco, it's illegal to discriminate against employees because of their weight and height.

But, for the most part, employees have no protection from appearance-based discrimination unless policies also single out workers based on their race, gender or age. Some employers say it's not discriminatory to require that employees conform to appearance standards.

"Employers are free to be unfair," says Bill O'Brien, a Minneapolis employment lawyer. "We saw it first on the playground, when the popular people who were the leaders chose other people like them as friends."

What began on the playground can have a profound impact on paychecks. In a recent analysis, the Federal Reserve Bank of St. Louis found that a worker with below-average looks tended to earn significantly less — on average 9 percent less — per hour than an above-average-looking employee. Those with above-average looks tended to earn 5 percent more than their average-looking colleagues.

Looking good on the job is an intangible asset in the same way that sharp technology skills or the ability to be a team player can give certain workers an edge.

It's important enough that Patti Pao, 40, a vice president at David's Bridal in Conshohocken, Pa., never goes to a meeting without putting on lipstick. It's also the reason that Brian Chernicky, 30, owner of San Diego-based Real Online Marketing, wears a pair of fake glasses when wooing clients.

And it's the reason Matt Kennedy, 24, a public relations account executive in Orlando, no longer wears his hair to work in a fashion that looks like a modified Mohawk.

"On the weekends," he says, "I wear my trendy clothes and jeans that are bleached out."