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Fat Burning Zone

If we could identify the exercise intensity that produces the highest rate of fat oxidation, then we could workout at this intensity and make dramatic improvements to our body's composition.

Low intensity sessions to burn off fat

There are two key variables that we need to know:

  1. Fatmax - the exercise intensity at which the highest rate of fat oxidation occurs
  2. Fatmax zone - the range of exercise intensities in which the fat oxidation rates remain within 10% of Fatmax

Research

Researchers from Birmingham University's Human Performance Laboratory attempted to pinpoint the exercise intensities at which fat metabolism is maximised in a study[3] of 18 male endurance cyclists with a training background of at least three years. Their work found that the Fatmax Zone is between 68% and 79% HRmax

Alternative research has suggested that when you cycle, swim, row or run at a modest intensity of only 50% VO2 max (about 69% HRmax), fat provides about 50% of the calories you need to keep going for the first hour or so. If you keep going after that, fat becomes even more generous, providing around 70% of the total energy after two hours and 80% or more if your work duration exceeds three hours. If you increase the intensity then the Fat contribution decreases - at 75% VO2 max fat provides 33% of the energy.

 

High Intensity sessions - just as good!

The implication from all this research (Anderson 2002)[1] is that if you wish to burn maximum amounts of fat then you should train in the 68 to 79% HRmax window. The reality is that if you train at higher intensities you can burn just as much fat.

If you cycled along at 50% VO2 max, fat would provide about 50% of the energy you needed to keep going. If you cycle along at 75% VO2 max, fat would provide 33% of the required calories. Thus, the slower workout sounds better from the fat breakdown perspective - or does it?

A moderately fit athlete exercising at 50% VO2 max generally consumes about 220 Calories during a 30 minute workout. If the same athlete works out at 75% VO2 max, 330 Calories are burned during the same period. Of course, 50% of 220 Calories and 33% of 330 Calories yield an identical number of calories coming from fat - 110 Calories.

Interval work may be the solution

Australian Researchers at the University of New South Wales and the Garvan Institute studied 45 overweight women over a period of 15 weeks. Three times a week the ladies cycled for 20 minutes, sprinting in bursts of 8 seconds followed by 12 seconds of easy cycling.

Professor Steve Boutcher, leader of the team, stated that the women lost 3 times more weight as other women who exercised regularly at a continuous pace for 40 minutes. The women in the study were said to have lost weight mainly from their legs and buttocks.

It is not clear as to how it works but interval training is far more response in getting the body to yield its fat.

Fat provides all your energy

If fat alone was meeting all your energy needs, you would not be breaking down carbohydrate during your workouts and as a result your leg muscles would be amply and permanently stocked with glycogen (assuming, of course, that your diet contained a normal carbohydrate content). Each time you ate, the carbohydrate from your meal would be processed and transported to your muscles. Your muscle cells would say, 'No thanks, I do not need more carbohydrate, I am already full.' The surplus carbohydrate from your meal would be converted to fat. Looks like a no win situation - as fast as you burn fat off it is replaced.

Effective way to lose fat

Most exercisers are time constrained to some degree and do not have hours to spend on low intensity sessions. When time is limited, there is little reason to train in your Fatmax Zone. If your overall goal is to get leaner, the bottom line is that Fat Burners are the best way to achieve it.

The most effective way to lose body fat is to burn slightly more calories than you take in, and to continue this negative energy balance over an extended period.

Medium-chain triglyceride (MCT)

MCTs are a class of fatty acids occurring normally in oily foods which require less energy for uptake and storage in the body and are easier to digest and absorb than ordinary fats. Research indicates that the consumption of MCT oil (14-20grm/day - 112-160 calories) could be a useful addition to the diet for athletes trying to lose or maintain body fat. MCT oil is commercially available.

Coconut oil and Palm oil are naturally rich in MCT but they also contain long-chain triglyceride (LCT). Studies have demonstrated a weight loss effect with a MCT/LCT mix - 14grm with a 12% MCT content (Hamilton 2008)[2].


References

  1. ANDERSON, O. (2002) You do have a fat burning zone, but do you really want to go there to burn off fat. Peak Performance, 164, p. 1-4
  2. HAMILTON, A. (2008) MCTs time to renew an old aquaintance. Peak Performance, 164, p. 8-11.
  3. Medicine and Science in Sports and Exercise, 34 (1), p. 92-97

Related References

The following references provide additional information on this topic:

  • CAREY, D. G. (2009) Quantifying differences in the “fat burning” zone and the aerobic zone: implications for training. The Journal of Strength & Conditioning Research, 23 (7), p. 2090-2095
  • ACORN, R. G. et al. (1994) "Algorithm for prescribing an exercise regimen to enhance fat burning and cardiovascular fitness." U.S. Patent No. 5,297,558
  • SNOW, M. G. et al. (2003) U.S. Patent No. 6,554,776. Washington, DC: U.S. Patent and Trademark Office

Page Reference

The reference for this page is:

  • MACKENZIE, B. (2003) Fat Burning Zone [WWW] Available from: http://www.brianmac.co.uk/fatburn.htm [Accessed

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