The Fat Burning Zone: I don’t get it!

Ariane,

as you’ve noticed, I’m wearing a heart rate monitor in our Slim & Strong workouts. My heart rate is very high during our classes, averaging 160-170 beats per minute (bpm) and a high of 190. I usually burn about 550-575 calories. I’m 5’2 and weigh 136 lbs. I have heard of the magical ‘fat burning zone’, which is a much lower heart rate. I usually spend about 10% of class in that zone, if that. It seems to me that you burn more calories at higher intensity and with a higher heart rate, so I don’t really get this ‘fat burning zone’ idea. Is this something I should be concerned about? is there a good way to monitor my heart rate to keep the intensity of my workouts effective once Slim & Strong boot camp ends in a week?

Thanks, Leslie

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Leslie,

the ‘fat burning zone’ is a very outdated way of looking at exercising. Unfortunately there are still trainers out there that suggest you work out at low intensity in order to burn body fat rather than making your workout effective. Those trainers are probably the ones that still preach what they learned more than 10 years ago and haven’t caught up with the latest and most effective training methods.
The key takeaway is that the higher the intensity, the more calories you burn. It is true that at lower intensity you burn more calories from fat and less from carbs in terms of percentages, but what matters is how much you burned overall and also how much of an after-burn effect you create (it’s also called EPOC, which is the a
mount of energy used by your body even after your workout is over).
If you go for a walk for an hour, you burn around 300 calories. Of those calories you burn about 40% from carbs, and 60% from body fat. If you run on the treadmill for an hour, you burn about 600-800 calories and about 60% from carbs and about 40% from fat (calorie burn depends on a lot of factors: your weight, your muscle mass, your level of fitness, your workout, whether you ate and what you ate before your workout, etc.)
What you need to know is that overall you burned a lot more on the higher intensity treadmill workout than with walking. Plus, you also will be burning calories after you’re done with your high intensity workout. During a strength training workout you’ll burn about 400-600 calories per hour – depending on how you train, and you’ll burn calories for at least 24 hours after you’re done because your body is repairing the microscopic damage you’ve created. Plus, the added muscle requires more calories just to stay on your body. That’s why strength training is more effective at changing your body in the long run – the results carry on – while cardio calories are burned only during the workout and not much afterwards. Plus, long and drawn-o
ut cardio workouts promote muscle loss and a stress response by your body that promotes fat storage. This is even more enhanced in people who are already quite lean and focus on cardio workouts.
The reason our Brooklyn Bridge Boot Camp and Slim & Strong workout sessions bring about changes so fast is because they are high-intensity-interval-training based. We push ourselves for short cardio intervals, then lift weights or use our own body weight for resistance. We combine strength and cardio so that your heart rate is elevated throughout the entire hour. You promote the release of adrenaline, which forces your body to use body fat from underneath your skin. You also promote the release of growth hormone, which keeps you young and lean, and you stimulate the growth of muscle, which burns calories, increases your metabolism even at rest and makes you leaner. At the same time you are burning through the glycogen stored in your liver and muscles, which then forces your body to use body fat for energy. That means you’re losing fat! Also, you’re improving your insulin sensitivity, which is a sign of great health because your body can utilize the carbohydrates you eat better rather than having them get stored as body fat.
To sum up the answer: whether you burn fat or muscle depends on how much body fat yu have, what and if you ate before your workout, how hard you work out and what other workouts you do. Cardio alone promotes muscle loss, especially with low body fat and a low-protein diet. If you have a decent amount of body fat to lose, focus on strength and cardio together, keep your carb intake low and your protein intake adequate, you will be in fat burning zone, regardless of your heart rate during an hour-long workout.
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