Leading on nicely from last week's post on a basic introduction to fat I am going to talk about how we use fat for fuel and how the endless cardio sessions really are not helping you lose the fat you don't want.
Before we try and dispele the myths let's talk about how the body makes energy for us to live and move. Our body uses an energy currency called Adenosine Triphosphate (ATP), The body produces ATP in three ways. There are two anaerobic (Without oxygen) energy pathways, the glycolytic system using glycogen and the ATP-Phosphocreatine system. Both are high intensity short burst systems that we will bring up in future posts. The system we want to discuss is the aerobic system (With oxygen) as this is the fat burning system, and where the fabled fat burn zone has been derived from.
You will see the Fat Burn button on most cardio machines in the gym, press it type in your age and weight and the machine will keep you in your fat burn zone based on your heart rate. This is usually based on the calculation of 220 minus your age as your estimated maximum heart rate and then a percentage spanning from 55% to 75% of that maximum depending on machines settings to give you your fat burn zone.
This is where you are burning fat predominantly for fuel, sounds great just keep in this zone and the fat will just melt away! That's why we see so many people on cardio machines for hours slogging away in a vain attempt to shift the flab, but it rarely works particularly as the diet generally doesn't back up the time spent at the gym, plus a few other issues.
We are burning fat as a fuel at all times to some degree and it is true that at lower intensity it is the dominant source of energy production, however the fat that is being used is not from your stored body fat it is already in the bloodstream as free fatty acids (FFA). Then we have to consider the fact that most people are not good at burning fat due to the overconsumption of carbohydrate and the body using glycogen as an easy to use fuel.
An example, if long low intensity exercise was really that good for fat loss then why do you still see overweight postmen? They are walking 5 or 6 days a week 5-8 hours a day, surely they should all be in great shape? You may be thinking but what about endurance athletes, they are thin? And you would be right, they are thin, but thin doesn't mean healthy. Look at most elite marathoners, they are generally very thin with little muscle mass, then take a 100 meter sprinter, which physique is more impressive? Many recreational runners are still carrying extra weight even though they are running 4 to 5 days a week, what is the answer run more? I would answer not more but faster and shorter and supplement with some resistance training.
But by going faster means higher intensity and so you shift to burning more glycogen for fuel? This is true but you don't stop burning fat, you never burn either fuel independently, you just shift the percentage but the total expenditure increases. The added intensity also fires up your metabolism and keeps burning after your workout, at the same time stimulating muscle growth and repair.
High intensity sessions can be hard, and they should be as the body has nothing to adapt to but they don't have to be very long making it easier to fit into your life, a 20 minute interval session done correctly is more than enough. I will do a post on this way of training with some ideas for your workouts next week.
I need to make a point that exercise is great and an important factor in a primal lifestyle, it should be functional,varied and most importantly enjoyable, it makes you strong, agile, flexible and fit but it has limited effect from a purely fat loss point of view. This is particularly true if you are still eating a high carbohydrate diet, your body will always go to the glycogen before the fat as it is easier to metabolize and then we need to consider the insulin released in response to this will suppress the fat burn potential. Also exercise makes you hungry, I often hear people leave the gym say "I'm starving", No wonder you have just depleted your glycogen store and your body saying give me more! Although it still has a plentiful supply of fuel in the fat stores, it is just not good at getting to them.
The best way to burn fat is to eat fat, as we said last week it is a great fuel but you have to adapt the body to using it. You can only do this by cutting down the carbohydrate content in your diet making the body into a fat burning machine all day long not just during workouts.
To conclude I am not shunning endurance athletes in anyway if you enjoy it then keep it up, hats off to your dedication. I am however pointing out that if fat loss is your goal then perhaps you should try another route and by that I don't mean go a different way!
Keep it Primal
Primal Blueprint - Mark Sisson
Eat Bacon Don't Jog - Grant Peterson