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Exercising at Lower Intensity Levels for Longer Durations
Fat-burning claim: Exercising at lower intensity levels and for a longer duration burns more fat than moderate- to high-intensity exercise. People who subscribe to this theory use some of the same facts above regarding the source of fuel for various levels of exercise intensity. Further adding "credibility" to these claims, many cardio machines have "fat burning" workouts or programs, which have you exercising at lower heart rates.
Fat-burning fact: While it is a fact that low-intensity activities use more fat as fuel, this theory doesn’t hold up unless you can devote several hours every day to exercise. It’s important not to confuse percentage of fat burned with total amount of fat burned. Let's look at three examples of fuel usage, at three different intensity levels, and see which actually burns the most fat:
High-intensity exercise (about 70% max heart rate): 33% of the energy you use comes from fat and 66% comes from glucose. You're burning about 600 calories per hour (200 calories from fat).
Low-intensity exercise (about 50-60% max heart rate): Your ratio of fat to glucose usage is about 50-50. You're burning about 350 calories per hour (175 calories from fat).
Sitting still (resting heart rate): 66% of the energy you use comes from fat and 33% comes from glucose. You're burning about 90 calories per hour (60 calories from fat).
Fat-burning tip: Most of us can only manage about one hour of high-intensity exercise, but could handle several hours of low-intensity exercise like walking. Exercising at lower intensity levels for longer durations only burns more fat IF you have at least two hours to spend on that activity. However, low-intensity exercise also offers fewer general health benefits and won't help you improve your cardiovascular fitness level. If you’ve got two hours to spend on cardio your best bet is to get the best of both worlds by doing an hour each of higher and lower intensity exercise.
Making Strength Training More Important than Cardio
Fat-burning claim: You’ve heard it a million times—muscle burns more calories than fat, even while you’re sitting still. So when it comes to losing weight, strength training is more important than cardio.
Fat-burning fact: Part of this is true. A pound of muscle, at rest, burns about three times as many calories as a pound of fat, which by nature is pretty much always “at rest.” But whether or not strength training should be the only (or main) focus of your fitness program depends on what the numbers really say. Continued ›
Dean Anderson has master's degrees in human services (behavioral psychology/stress management) and liberal studies. His interest in healthy living began at the age of 50 when he confronted his own morbid obesity and health issues. He joined SparkPeople and lost 150 pounds and regained his health. Dean has earned a personal training certification from ACE and received training as a lifestyle and weight management consultant.
See all of Dean's articles.
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