Why Exercise Does Not Equal Weight Loss

The truth is: exercise does not always take off weight. Sometimes it does. But sometimes it doesn't. Jane Brody directs us to the August/September issue of ACE Certified News (published by the American Council on Exercise), where Ralph La Forge, managing director of the Duke Lipid and Disease Management Preceptorship Program at Duke University Medical Center, has compiled a detailed analysis of the various factors that influence the effect of exercise on weight loss. Here's where it gets complicated, (readers are advised to read the entire story in the New York Times) but to make a more complicated story less complicated, several things greatly influence the number of calories burned during exercise. One is the type of activity you do. La Forge tell us that weight-bearing activities that work against gravity — aerobic activities like walking, running, cross-country skiing, dancing, skating and stair-climbing — use proportionately more calories at a given level of effort than swimming, cycling or water aerobics. He also notes that how skilled you are at your chosen activity also influences the calories burned. Those less skilled make unnecessary movements or have to work harder at the activity, using more calories an hour than those who perform it efficiently. That may sound like it is an advantage to be unskilled, but there is a significant downside: Those with less skill tend to tire faster and thus spend less time at the activity. Another factor in caloric burn, says LaForge, is the increased number of calories the body uses after a workout. Both aerobic and resistance exercises raise energy expenditure over the next 12 to 24 hours, but the range is great — from 10 to 150 calories, depending on the type of activity and how long and vigorously it was done. Finally, and most unfair, is genetic influence. Brody tell us that some people are born with  a higher resting metabolic rate or produce more fat-burning enzymes than others. People with a low percentage of slow-twitch muscle fibers seem less able to burn fat in skeletal muscles and thus may have a harder time losing weight through exercise. Even more unfair, she says, women tend to burn more fat under the skin but have a harder time getting rid of abdominal fat than men do.