Myths and Realities of Fat vs Carbohydrate Burning
- Important and elegant studies by Dr George Brooks from the University of California, Berkley, showed that the body uses fats mainly for energy at rest and low-intensity exercise37,38.
- At exercise intensity above 65% maximum effort, the body switches abruptly from fat use to carbohydrate [glucose/glycogen] use to fuel muscle contraction.
- So this must seem like an easy solution to fat loss, exercise to your heart's content at a low intensity and you will blast away fat!
- To reinforce this way of thinking, companies that develop exercise equipment will have an electronic indicator showing you are in the "fat burning zone" which will have you work at 30% - 60% of maximum effort.
- So many people spend a great deal of time on treadmills or steppers, rowers etc. thinking they are losing a great deal of fat.
Low vs High Intensity Exercise
- Let's say you devoted 15 minutes to a low-intensity exercise at 30% - 50% of your maximum effort and sometime later, you did 15 minutes of high intensity exercise at over 65% maximum effort --- working out that you will have used more calories in the high-intensity exercise than the low-intensity workout is readily apparent.
- What is more important than the fuel that you use during exercise is the amount of calorie burning after exercise known as the after-burn effect.
- The other problem with steady-state exercises like running, treadmill, steppers is that you will over time develop muscle atrophy. To see why you lose muscle mass over time with steady-state exercises - Click Here
Is the after-burn effect worth it? - 773 kcal energy loss in 48 hours and 8.8 kg fat loss
a year!
- In a study by Schuenke et al 2002, a resistance training circuit that lasted
onl y 31 minutes and included bench press, power cleans and squats using a 10 RM load i.e. a load that could be lifted to exhaustion in 10 repetitions of an exercise, found that the body's metabolic rate was increased up to 48 hours after the exercise39.
- This equated to a massive 773 kcal expended post-exercise39 --- in other words you could have been sitting down watching TV after the high-intensity exercise routine and have lost 773 kcal of energy or 85 grams of fat.
- If you controlled your diet over this period of time by decreasing calorie intake and made sure your intake of protein was adequate to maintain muscle mass , then the vast majority of this post-exercise after burn would result in fat loss.
- If you exercised twice weekly then you will have lost 170 grams of fat in this post-exercise period per week and you will have lost 8.8 kg of fat per year.
