In this article: Exercising in front of a mirror How long to wait after eating to exercise Why lift weights? Ideal body-fat percentages Additional info Chart: Determine your Body Mass Index Sorting out diet drugs

How important is it to exercise in front of a mirror, and why?
Mark Quinn, San Francisco

Foreman: Many gyms have mirrors just so people can see how good they look. But working out in front of a mirror can be useful, too. In boxing, that mirror can be your best friend, because you can see if you are making mistakes -- dropping your hands or holding your chin up.

Mirrors are good for checking out your form. When you're working on building a certain muscle, you want to watch your technique. But mirrors can also be distracting if you're seeing other people or looking at yourself and you don't concentrate on your training. If so, check your progress and technique with mirrors occasionally.

How long should I wait to exercise after eating a small meal? I use a NordicTrack and treadmill, lift weights, stretch and jog.
Jerry Draws, Omro, Wis.

Dr. Mitchell: Wait as long as it takes you to put on your exercise clothes. Seriously, if you follow a routine of regular, moderate exercise, a small amount of food just before activity is no problem. A small meal: a sandwich, salad, fruit -- anything where you're not sitting down to several courses.

It does make sense to give your body 1-2 hours after a large meal to begin digestion, especially if you are planning intense activity. The exception: yoga and other flexibility exercises that may require you to lean forward. That kind of activity should be done on an empty stomach (three hours after a meal).

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Why lift weights?

As you age, your lean body mass shrinks and your metabolic rate (the rate at which you burn calories) slows. You can eat exactly what you ate 10 years ago and weigh the same but have a higher body-fat percentage. More fat carries risks, including diabetes, arthritis, back pain, high cholesterol and high blood pressure. It even can raise your risk for certain cancers. Strength training lowers body fat by building lean muscle mass; 20 minutes, 2-3 times a week, is all you need. Get body fat measured at a gym or health club. That number is much more important than your weight. --T.M.