I have put together an article for all the people out there who want to optimize their exercise sessions (walking, swimming, running) for achieving the maximum fat burn rate (losing your body fat should be your primary weight loss goal). At the end of the day it is all about the total calories burned. If you are a very busy individual who is already in good physical condition, you might achieve better results with higher intensity exercise sessions (because of the shorter duration). But for most of my readers, longer sessions of lower intensity exercise will be the optimal fat burning solution.
Our first goal is to determine the heart rate that will make you burn the highest percentage of body fat. The first thing you will need to do is determine your maximum heart rate (mostly age related) and then apply a certain percentage to it to determine your optimal fat burning heart rate. Once the numbers are crunched, you will need to learn how to properly pace your exercise sessions to keep your heart rate as close to this (theoretical) optimum. It is much less complicated than it sounds, so let's get to it.
How to calculate your maximum heart rate?
Maximum heart rate is the peak pulse your body is able to (safely) handle for a short period of time. Even if you tried to persist at this pace to see if your heart would jump out of your chest, you would quickly be so out of breath that you would be forced to slow down. And if I were you, I wouldn't try testing this in real life too much, for obvious safety reasons.
Your maximum heart rate is largely age dependent and you can calculate it by subtracting your age from 220 (if you are a man) or from 226 (if you are a woman). If you are a 45 year old man, your maximum heart rate would be 220 - 45 = 175. If you are a 30 year old woman, your maximum heart rate would be 226 - 30 = 196. Simple, right? Now go ahead calculate your own maximum heart rate.
The maximum heart rate is an estimate and it is evident from the formula that it decreases with age. This seems logical enough. If you are 20 years old young body is able to handle much more intensity than if you are 70 years young. But still, age is not the only factor here. If you are extremely overweight and have been sedentary for the last couple of years your heart your body will obviously not be able to handle the same (calculated) maximum heart rate as if you have been running marathons for the last couple of years. But you don't need to worry too much about this, since you won't be training anywhere near as intense. The only take here is that this is an estimate and not an exact science.
How to calculate your optimal fat burning heart rate?
Ok, now we that we know how to calculate the maximum heart rate we need to calculate our optimal fat burning heart rate. To determine our optimal fat burning heart rate, we will need to calculate the lower and the upper end of your “fat burning zone”. The usual story goes like this. If during exercise training you manage to keep your heart rate between 50% - 70% of your maximum heart rate, you will also burn the highest percentage of calories from your body fat. As long as you stay in this range, about 85% of your total calories burned will be coming from your body fat stores.
Let's get down to calculations. In our precious example we calculated that if you are a 45 year old man, your maximum heart rate would be 175 and if you are a 30 year old woman, your maximum heart rate would be 196.
The fat burning zone for a 45 year old man would be calculated as follows:
- low end of the fat burning zone: 50% of 175 (175 * 0.50) = 88
- high end of the fat burning zone: 70% of 175 (175 * 0.70) = 123
And for a 30 year old woman:
- low end of the fat burning zone: 50% of 196 (196 * 0.50) = 98
- high end of the fat burning zone: 70% of 196 (196 * 0.70) = 137
In order to maximize the percentage of calories burned from fat, our made-up man needs to keep his heart rate between 88 and 123 and our non-existing woman needs to keep it between 98 and 137 beats per minute.
How to pace yourself properly during exercise
The first method of doing this is by feeling your pulse with your fingers on your neck (you will have to locate the exact spot on right below your jaw on the left or the right side of your throat) or below your wrist (this one is a bit trickier to find, so you should probably go for the neck). Once you find the pulse, you need to count the beats for exactly sixty seconds (look at your watch while counting). If the number of beats falls somewhere in between the low and the high end of your fat burning zone, you are golden. If you counted too few beats (like less than 88 for our male example) you need to speed up the pace. If you counted too many beats (like more than 123 for our male example) you need to slow down the pace of exercise. While this is a free method, it is not really practical, plus you will probably need to stop with the exercise, just to be able to take measures.
A much more convenient method would be buying a heart rate monitor (also called a pulse meter) which is really not that expensive. It looks like a watch and the better ones come with a sensor belt you strap around your chest. Once you familiarize yourself with it, you will instantly be able to check if your pulse is still in the fat burning zone by simply glancing at your new “watch” without having to interrupt your exercise. You can even set up your heart monitor in a way to start warning you (with an annoying beeping sound) as soon as your pulse falls below or rises above the fat burning zone.
The fat burning zone (in)accuracy
Like I said before, this numbers are all estimates and while you can become really good at targeting your heart rate, the only reliable way of determining your “exact” optimal fat burning heart rate would be to have the measurements done on your own body. I have found a study which came to somewhat different results than what the general consensus seems to be. According to their results, the fat burning zone extends from roughly 60% to 80% of the maximal heart rate (not from 50% to 70%). And their results also suggest that the body fat zone and the aerobic zone are overlapping, which would suggest that training for aerobic fitness and maximum fat burn rate are not exclusive (but this discussion would be way beyond this article).
However, the same study admits that the differences in results between individuals were quite big. Besides that they used a relatively small sample (36 people) of not exactly average people (relatively fit runners), which raises the question whether their findings are applicable for the general public. My personal opinion is that it would be better to stick to the general consensus for fat burning zone being between 50% - 70% of your maximum heart rate. Or if you insist, you can stay between 60% - 70% of your maximum heart rate (where findings from the study and the general consensus overlap).
The fat burning zone is a great guideline as far as I'm concerned, but getting all "technical" with things is more of a personal choice than a necessity. One rule of thumb you can use to avoid all the calculations and measurements would be doing your exercising at a pace where it is still comfortable for you to have a conversation. Or if you are usually alone, you can try doing it at a pace where you are still able to comfortably breathe through your nose (bring a tissue if necessary). The most important thing is to discover the type, pace and duration of your exercises that will enable you to burn the most total calories while not exhausting you to a point where you are unable to repeat it the next day (or whatever other interval you have set for yourself). Exercising anywhere near your (estimated) optimal fat burn rate will be of great help with this.