Dear Doctors: I’ve heard that when you’re on a diet and you decrease caloric intake by a lot, your body will start to consume muscle for energy. It that really true? How can you lose weight and not wind up losing muscle?
Dear Reader: Discussions about losing weight typically focus on pounds, as in, “I want to lose 10 pounds.” The important follow-up question here is: pounds of what? Work up a sweat with a vigorous set of tennis, and the scale will show you’ve immediately dropped a few pounds—of water weight. You’ll gain it right back with your next beverage. (A quart of water weighs 2 pounds, in case you were curious.)
Diets that involve a drastic calorie cut do lead to weight loss, but participants wind up burning not only fat, but also significant amounts of lean muscle. That’s a bad idea, because we rely on our muscles for both strength and endurance. Muscle tissue also plays an important role in resting metabolic rate.
The answer to the “pounds of what?” weight-loss question is, of course, fat. When we set a weight-loss target, the goal is to lose fat. Or, to view it in more useful terms, we want to achieve a more healthful ratio of lean tissue to fat. Achieving and maintaining a healthful weight has many benefits, including reducing the risk of diabetes, high blood pressure, coronary artery disease, depression and even certain cancers. And, while it’s tempting to try some of the more extreme low-carb and high-fat diets that are now popular, which promise swift and painless weight loss, we believe a moderate approach yields better and more sustainable results.
In order to maximize fat loss and minimize the loss of lean muscle mass, you need a three-pronged approach. This begins with cutting back calories enough that you’re operating at a slight deficit, but not to the point that your body thinks it’s starving. A recent study in the Netherlands followed volunteers on a five-week diet of 500 calories per day, and those on a 12-week plan of 1,250 calories per day. Both groups lost the same amount of weight—about 19 pounds. However, the crash dieters lost almost three times as much muscle mass as those who followed the more moderate weight-loss plan.
To stay healthy as you lose weight, eat a wide range of fresh foods, with a focus on lean proteins, healthy fats, and fresh fruits and vegetables. Take care to avoid simple carbohydrates and processed foods. You want a diet that, once you’ve reached your goal weight, you can continue to sustain.
Finally, it’s important to incorporate two kinds of exercise into your daily life: cardio and resistance. Cardio helps to burn fat, and resistance maintains and builds the lean muscle mass that you want to conserve. Again, the aim here is a new set of habits that you’re willing and able to maintain even after you’ve reached your goal weight.
Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.