Being overweight or sloppily dressed is worse for your career than being a poor performer.

I'm not saying this is fair, I'm saying it's true. So manage your weight, and manage the image you project at work, and you'll do wonders for your career.

If you doubt that your image can inhibit your career, think about this: According to a 2005 study by the Federal Reserve Bank of St. Louis, good-looking people make more money than average-looking people for doing exactly the same work.

Before you get up in arms over how unfair it is to discriminate against people who are overweight, consider that there may be some rationale behind it. If you're overweight, you're probably not exercising every day. But regular exercise increases peoples' ability to cope with difficult situations in the workplace and, according to University of Illinois kinesiology professor Charles Hillman, might even make people smarter.

And the same self-discipline we use to make ourselves exercise regularly and eat in moderation carries over into other aspects of our lives. This is probably why, in a study from Leeds Metropolitan University, people who exercise regularly were found to be better at time-management and more productive than those who don't.

So don't kid yourself that if you do good work it won't matter if you're overweight. It's sort of like people who have messy desks: The perception is that they're low-performers, poor time-managers, and not clear thinkers. This might not be true at all, but the only thing they can do to overcome the perceptions of their coworkers is clean their desks.

Read the rest on Yahoo Finance.