I get a lot of emails with questions about health and fitness (and I love getting them…so keep ’em coming!). I got one a little while ago and I have been meaning to post on it.
Here’s the email I received:
I had a debate with a friend and wanted to check w/ an expert! She is purposefully lowering her heart rate during exercise to stay in the fat burning zone b/c she is in good cardiovascular shape and wants to burn fat first and foremost. I thought you just push yourself and in the cardio zone you burn both. Are we both wrong? Or who is right?
I’m sure most of you have heard of the “Fat Burning Zone” and the “Cardio Zone”…if you’ve ever used any cardio equipment you’ve probably seen both of these terms listed right on the machine with accompanying heart rates based on age. During some of the programs the machine actually tells you to slow down if you are going ‘too fast’.
For awhile it was drilled into us that we should keep our heart rate at a certain level in order to make sure that we are burning the most fat. Hopefully you have gotten over this by now and you realize that if you’re looking to lose fat, total caloric expenditure should be the main focus/goal of your exercise.
Although your body does indeed burn a higher percentage of calories from fat in the ‘fat burning zone’ or at lower intensities, you still burn a greater number of overall calories at higher intensities. The chart below details the fat calories expended by a 130-pound woman during cardio exercise (MHR stands for Maximum Heart Rate):
| Low Intensity – 60-65% MHR | High Intensity – 80-85% MHR | |
| Total Calories expended per min. | 4.86 | 6.86 |
| Fat Calories expended per min. | 2.43 | 2.7 |
| Total Calories expended in 30 min. | 146 | 206 |
| Total Fat calories expended in 30 min. | 73 | 82 |
| Percentage of fat calories burned | 50% | 39.85% |
Source: The 24/5 Complete Personal Training Manual, 24 Hour Fitness, 2000
In this example, the woman burns more total calories and more fat calories at a higher intensity. The percentage of fat calories burned during the low intensity exercise is higher, but not nearly high enough to make it a better choice than the higher intensity exercise.
So what do you do now?
Make strength and intervals the focus of most of your workouts. 🙂
Love your long runs or trotting along on the elliptical watching your favorite show? There is absolutely no reason that you can’t incorporate some steady state cardio workouts into your program. Just know that those are probably not the days where you end up blasting the most calories and burning the most fat.
Keep in mind that people’s heart rates (and maximum heart rates) differ quite a bit from person to person. By sticking to a generalized recommended target heart rate, many people would be either under-training (those with high max heart rates wouldn’t push themselves hard enough) or over-training (those with low max heart rates might push themselves too hard).
In summary…
if you are healthy and cleared to work out by a doctor and you’re looking to burn fat, your best bet is to work hard! There’s no good reason to slow down if you’re working out and feeling great!
What is your favorite fat-blasting workout?
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