Food & Fitness: Slowpokes burn more calories
The weight-loss race may go to the speed-challenged tortoise, not the hare, according to new obesity research. Contrary to much past fitness advice, leisurely walking—instead of brisk walking—combined with a low-impact cardiovascular workout, such as biking or swimming, may be a much better formula for overweight exercisers trying to lose weight than vigorous walking and high-impact workouts. Strolling about 2 miles per hour actually burns more calories than the often prescribed brisk 3 mph. Strolling has the added benefit of reducing impact on the knees by 25 percent.
"We were really surprised," says Ray Browning, a researcher at the University of Colorado and the lead author of the study in Obesity Research. "The variable people have been ignoring is that you are less economical when you walk at a slow speed." Biology dictates that humans tend to walk automatically at the speed that conserves their energy the most. If walking a mile at a person's normal speed takes about 20 minutes, then slowing down means the same mile takes, say, 25 minutes.
"When you slow down, then you become less efficient and you walk longer, so you burn more calories," explains Browning, who adds that leisurely walking is great for people trying to lose weight. "The key is walking longer." Browning says that most doctors and obesity experts have advised people to walk briskly because of the heart benefits. A vigorous walk increases the heart rate, builds heart muscle, and tends to reduce blood pressure. "The effort of brisk walking is enough to improve cardiovascular fitness," says Browning. "But there's another side to the equation. And that's the need to minimize the risk of musculoskeletal injuries while using more calories. What we found is that obese women, for example, who do brisk walking for exercise have seven times the risk of developing osteoarthritis of the knee." Browning and his Colorado colleagues believe the medical community's exercise prescription, certainly for most overweight or obese folks, may need an overhaul. "We're creating the public health perception that what people have to do is go out and walk briskly for 60 to 90 minutes, and most people just can't do it, and if they do, lots of them get injured." The Centers for Disease Control and Prevention reports that some 25 percent of sedentary people who begin a brisk walking program, end up injuring themselves. Ironically, many return to sedentary lives. "And here the whole idea was to increase physical activity," laments Browning. "So what we're recommending is that rather than overweight people using brisk walking as their primary form of exercise, slow walking is great for burning calories while protecting the joints. Then, use other forms of low-impact aerobic activity—cycling, swimming, or elliptical training—to get the heart rate up and increase cardiovascular fitness."
An avalanche of medical studies have pretty much proved that exercise confers a variety of benefits no matter what people's weight. But finding the safest way for the majority of couch potatoes to get active is the newest challenge facing obesity experts. Browning's research points in a new direction. Maybe that old custom of a leisurely stroll after dinner was better for one's health than anybody thought.