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.

What makes this information particularly troubling is that so many people say they can’t make time to exercise and eat right because they need to work instead. In fact, if you’re overweight, you should probably put aside some of your work, accept that you won’t be performing as well at the office, and manage your image more closely by going to the gym.

That’s right — get rid of that perfectionist streak, do a little less work, and use that time to make yourself look better. People will perceive that you’re doing better work anyway. So instead of rationalizing why you can put work ahead of taking care of your health, start acting like a healthy person. Go to the gym at lunch, or leave work at 5 to hit the gym. Reorganize your schedule to make health a priority and your coworkers will respect you for it.

Here’s something else: Dress like you care. Building a strong brand for yourself is the only way to create a stable career in today’s workplace. You’ll change jobs often, and what influences your ability to get new jobs most is the image you convey. People judge that before they judge one word that comes out of your mouth.

I didn’t have a weight problem when I owned my first company, but I did have an image problem — I was younger than almost everyone, and my mentor told me my age was creating problems. So I hired an image consultant to drag me around town and spend lots of money until I looked more grown up.

I still worry about image issues today — everyone does, no matter where they are in their career. It’s just that today I worry less about looking older and more about what shirt is right for an appearance on CNN. The point is that issues of image are ongoing in a career that matters.

So don’t be overweight and don’t dress carelessly. These are just as detrimental to your career as doing your work poorly. And if my bringing this up makes you angry, consider being more forgiving, because anger is a risk factor for obesity. Besides, forgiveness makes people more resilient to difficulties because it’s about seeing the world in a positive light — which is, of course, also good for your image.