The Fat Burn Zone?

Hop on any treadmill, elliptical, bike or any other piece of cardio equipment and it is sure to greet you. A bright and colorful graphic telling you exactly what heart rate you need to get to in order to burn your fat right off. But does this really work? The conventional wisdom in exercise science has long been that weight loss requires sustained, moderate aerobic activity. The “Fat Burning Zone” commonly recommended on cardio equipment follows this model. For example, a treadmill may recommend that a 40 year old maintain a heart rate of 111 beats per minute (bpm) in order to burn fat like a bonfire. Using an age predicted maximum heart rate equation, this would work out to be around 42% of a 40 year old’s Heart Rate Reserve (HRR). HRR is a useful method of calculating exercise intensity that accounts for a person’s baseline fitness by factoring resting heart rate into the calculation. The thing is, 42% of HRR is widely considered to be at the low end of moderate intensity. This is the intensity at which you can read a book, hold a full conversation with a friend and maybe even sing along with your iPod. Would working harder have a benefit for weight loss?

A thorough review by Shaw et al. in 2009 of 43 randomized, controlled trials says yes. As you probably assumed, people who altered their diet and exercised lost the most weight. But pooled results for over 300 participants showed that people who exercised at a high intensity achieved increased weight loss over those who exercised within the “Fat Burn Zone.” The reason that the myth of the “Fat Burn Zone” persists is that there is some truth to it. During a long, moderate workout, your body is more likely to use fat cells as a fuel source; literally burning fat as part of the metabolic pathway. But after this type of moderate workout, your body can return to a normal, resting state fairly rapidly and your calorie expenditure for the rest of the day is not tremendously altered. More intense activity, including cardio and resistance training, does not burn as many calories during the workout and most of the energy comes from sugars. However, this type of exercise greatly increases your oxygen consumption even after you finish your workout. Schuenke et al. in 2002 found that after an intense resistance training session for example, this period of increased energy expenditure lasts as long as 38 hours. Oxygen consumption is directly correlated to the amount of calories burned so one intense exercise session can increase your ability to lose weight over a day after you exercise! No wonder that the authors of the review concluded that “vigorous activity is more effective than moderate or light intensity exercise in inducing weight loss.”

This has huge implications on your workout if you are trying to lose some pounds, tone up or even win the Lose It! grand prize. Try to incorporate high intensity workouts by doing intervals during your cardio workouts and adding in some resistance training circuits. Keep in mind that high intensity exercise is not for everyone and if you are new to exercise or have always done moderate activity, you should talk with a Personal Fitness Trainer. We can create a program that allows you to reap the benefits of high intensity exercise in a healthy, sustainable and enjoyable manner.

Please contact Hunter Spencer if you have any questions or would like to set up a high intensity weight loss routine. Good luck with your weight loss goals and enjoy your newly intensified workouts!



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