By Eric Heiden M.D.
Tribune Media Services
Jen had been obese, had gastric bypass surgery and lost 80 pounds. She was walking five or six times a week — about 25 miles — and had started doing marathons. Then she started lifting weights twice a week to add some resistance training to her routine to help reduce her abdominal fat and her risk for heart disease. Suddenly, she started gaining weight. Jen got stressed and stopped lifting weights. When she came in for her next checkup, exercise performance physician Max Testa, M.D., asked her, “Why did you stop lifting weights?”
“Because I was gaining weight,” she said.
“But how did you feel when you were putting on your clothes?” Testa asked.
“Actually, they were loose,” she admitted. “But I was getting heavy. Since I’m always looking at my weight, the biggest stress is when I see my scale going up.”
In fact, Jen was gaining muscle — lean body mass — which is good for weight loss in the long term because the more muscle you have, the more calories you burn. She was building lean body mass, and lean body mass weighs more than fat, so weight gain is a necessary phase to go through. Unfortunately, by the time Dr. Testa saw her, she had not been lifting for a while and had already lost the lean body mass she had gained through strength training and needed to start over from the beginning.
That’s the trouble with using weight to measure your success. Gauging your progress in losing fat and gaining lean body mass only by weighing yourself can be misleading. Your scale doesn’t differentiate a pound of fat from a pound of muscle.
A measure that is often used to assess your baseline before starting a diet and/or an exercise program is the Body Mass Index. BMI is not your body composition. Your BMI is a ratio that uses your weight and the square of your height to determine a number that correlates to your body density.
Think of a marathoner, tall and light. He will score a low BMI. However, a short bodybuilder with little fat but a lot of “heavy” muscles will score a high BMI. Measuring your BMI is better than just measuring your body weight. By considering the additional factor of height, you learn more about yourself. Two hundred pounds of body weight impact a 5-foot-2-inch frame differently than a 6-foot-5-inch person.
Researchers also use BMI to compare groups of people of different height and weight. For example, we learned that in women over age 50, a low BMI increases the risk of osteoporosis, and that a BMI above 25 goes hand in hand with increased risk for heart disease. We could not delineate those risks based simply on women of a certain weight. In athletes, BMI also tells us a lot about performance. A cyclist with a BMI of 19-20 would be a great climber but will suffer when going fast on flats with a strong headwind.
You can find your BMI on my website, www.fasterbetterstronger.com.
Use the chart appropriate to your gender, then find your BMI using your height and weight, and make note of the number. The shaded areas indicate the healthy BMI range.
Eric Heiden, M.D., a five-time Olympic gold medalist speed skater, is an orthopedic surgeon in Utah. He co-authored “Faster, Better, Stronger: Your Fitness Bible” (HarperCollins) with Max Testa, M.D., and DeAnne Musolf. Visit www.fasterbetterstronger.com.
This column was printed in the October 23, 2010 – November 6, 2010 edition.
