The Best Heart Rate For Fat Loss? Whichever One That Puts You in a Calorie Deficit
As many of us start our new year resolution goal that most commonly comes up usually involves a change to our body composition. From trying to lose some Christmas weight to getting fit again many of us turn to exercise as a way to lose weight. If anyone has ever stepped onto a treadmill or other cardio machine you'll often see a heart rate chart. And there you'll see the 'fat burning zone'.
It seems too good to be true. Just exercise at this intensity or heart rate range and your body fat will burn away. Unfortunately, the concept of burning fat during exercise has been widely misunderstood and used to confuse people. So let's take a dive into what it actually means.
As you can see from this chart when we exercise at lower intensities, our bodies do utilise fat as fuel. However, if you look at these sources of fat these come from the fat already in our blood and our muscles. This is something completely different to our body fat stores. This system allows us a continual supply of energy as we exercise. Then as our intensity increases, the carbohydrate stores in our bodies are used. But these won't last as long as your fat stores. The average body holds 600g of glycogen which equates to 200kcal. Compare this to the 2000-300kcal of fat stored I your muscles its a small amount. However what sets these apart is the speed they can be utilised as fuel. Muscle stores of glycogen (from carbohydrates) are utilised quickly which is good for intensive exercise, whilst fats are slower to be converted which benefits us during slower activities. So how does this impact our body fat levels?
Simply put, converting body fat (adipose tissue) to energy is an even slower process. On top of this because we're constantly refuelling through meals and snacks. So what has the biggest impact on our body fat is an energy deficit where we put in less fuel than we burn.
As I said before, this misconception has been jumped on by a whole host of people in order to sell a particular diet or lifestyle. This is particularly apparent in the advocates of fasted cardio and the keto crowd. Excercise before eating burns fat they say? Well yes because your glycogen stores are lower as you haven't eaten many carbs yet. Eat fat to burn fat? Well yes, that's because its the only fuel your providing. Just like if your eat loads of carbs your going to burn more carbs. But what neither of these care to tell you is how this is independent of your adipose tissue which won't change without an energy deficit.
So if youv'e come across any other things in the world of fitness and nutrition that seem confusing please fell free to get in touch and I'll gladly clear them up.
Fundamentals of glycogen metabolism for coaches and athletes
Adrenergic regulation of lipolysis in situ at rest and during exercise.