What is the optimal fat burning heart rate when it comes to exercise, losing fat and getting fit? Unfortunately, it’s not a straightforward answer because myths and misinformation still persist.
In the past, when the aerobics craze first hit, and it was determined to be the best way to burn fat, the heart rate that will reduce fat was considered to be the percentage of maximum heart rate at which most of the calories burned came from fat.
Studies showed that the highest percentage of calories burned that came from fat happened when exercise was performed in a steady state manner between 55% and 70% of a person’s maximum heart rate, what became known as the optimal fat burning heart rate.
These studies also showed that the fat burning “zone” happened about twenty to thirty minutes into the workout.
Thus began the aerobics crazy of people endlessly pedaling a stationary bike, or jogging, albeit slowly, on a treadmill for thirty, sixty, ninety minutes or more, all within this rate of 55% to 70% in order to maximize the number of calories burned from fat.
This idea was also very appealing to people. After all, intense workouts were, well, intense! They were hard work! Why do that when you can choose easy as the better option? Sounds great, right?
Unfortunately, this magical fat burning rate for the heart was just a myth. At least, if you wanted to exercise more efficiently and get the most bang for your buck in terms of your fat loss results. Which is what most people want. This fat burning zone may be easy but it also kept people from seeing results as they were just spinning their wheels.
Let’s take a look at how the body burns calories for fuel during exercise. Simply put, the body burns glycogen and fat for fuel. Glycogen is the carbohydrates stored in the muscles and the liver.
The reason the 55% to 70% of maximum heart rate became ‘optimal’ for burning fat is because more calories are burned from fat stores at lower intensity levels relative to the glycogen that is used.
Okay, so that sounds great, right? Not so fast. After all, lower intensity is just sitting around the house. Or sitting at a desk all day at work. People might be burning more fat as fuel they they are not burning many calories at all.
As exercise intensity increases, and the percentage of maximum heart rate gets higher, a trainee will burn more and more calories from glycogen as opposed to fat. Studies have shown that at about 50% of the maximum heart rate the average person will burn sixty percent of calories from fat and forty percent from glycogen.
As the percent of maximum heart rate hits seventy-five percent, the percent of calories burned from fat falls to thirty-five percent, while glycogen calories jumps to sixty-five percent. This seems as if the more intense the workout, the less fat a person burns. And who wants that? But does that makes sense? The confusion lies in relative versus absolute calories burned. Let’s say one person exercises at 50% of their max heart rate and another trainee works out at the higher intensity of 75%, for an hour.
The 50% trainee burns 240 fat calories and 160 glycogen calories for a total of 400 calories burned. The 75% trainee burns 280 calories from fat, only 40 fat calories more while working a lot harder than the first trainee. But the second trainee also burns 520 calories from glycogen stores for a total of 800 calories burned.
It’s the total amount of calories burned during exercise that matters when it comes to burning fat off the body, not the number of fat calories burned. But it gets even better for the higher intensity workout. When exercising at a low intensity, there is no after burn. This refers to calories burned because of the workout but after the workout is over. However, when training at higher intensity levels, studies have shown that the metabolism can stay elevated for as much as thirty-eight hours after exercise. This means the trainee is burning even more calories without exercising.
One study at the University of Southern Maine,looked at this low intensity versus high intensity battle. One group cycled at a low intensity for three and a half minutes. The higher intensity group ran three different 15 second sprints as fast as they possibly could.
There was a huge difference in calories burned. The low intensity group burned twenty-nine calories during the three and a half minute workout. The spring group? Only four calories were burned. However, the study then added in the extra calories burned after the workout. The low intensity group burned thirty-nine more calories but the sprinting group burned sixty-five more calories.
The sprinting group exercised for forty-five seconds, while the low intensity group exercised the entire three and half minutes.
When it comes to the best heart rate that will take off the fat, the higher the intensity the better, all else being equal. This means performing high intensity interval training instead of steady state, low intensity cardio. Don’t worry about the actual heart rate number. By performing intense intervals, the heart rate will take care of itself.