Why Exercising for Weight Loss in Your ‘Fat Burning Zone’ is a Waste of Time


Have you ever heard a personal trainer or fitness professional say that to maximize fat loss you need to maximize exercise time in your “Fat Burning Zone”? Also have you noticed that just about any piece of cardiovascular exercise equipment has a “fat burn” program spaced between the interval and random programs? What is the so-called Fat Burning Zone anyway and why should you look for better options to help you maximize your fat loss results? This article provides some basic information on the fat burning zone and why interval-type training might be provide permanent results faster.

The fat burning zone defined

The Fat Burning Zone (FBZ) is an intensity (e.g. walking speed) of aerobic -type exercise that concentrates the use of fat as a fuel. Exercise intensity is typically measured by monitoring your heart rate, so exercising at about 65% of your heart rate max/HR max (220 – your age) places you in the “zone”.

Energy/metabolic contributions while exercising

Exercise intensity determines the relative contribution of different energy sources (carbohydrate, protein, fat) to fuel it. For example, high intensity exercise like running and sprinting rely more heavily on the use of carbohydrates than lower intensity exercise like walking in the zone which relies more on the use of fat.

Energy metabolism works on an exercise intensity continuum – that is at any intensity never does your body make use of a single type of fuel. For example, even in an all-out sprint some of your energy yield will come from fat and protein, but the large majority will come from carbohydrates. Similarly, even in the fat burning zone a percentage of your energy will come from carbohydrates and protein, but a much larger contribution will come from fat.

The basic rule is the higher the exercise intensity, the higher the relative contribution of carbohydrates to total energy expenditure and vice versa for fat – so it is in fact true that at the FBZ intensity, fat will be the maximal contributor of calories burned during the exercise session. (If I have confused you read on for an explanation).

For the casual exerciser, the FBZ is essentially useless

Here’s why:

Fat and weight loss is directly dependent on caloric (energy) balance – in other words if your total calories (food calories – exercise calories burned) in a day are less than the amount needed to maintain your current weight, you will lose weight; if you consume more energy that what you need to maintain your current weight, you will gain weight.

Your body doesn’t care where the “exercise calories burned” come from – whether from carbohydrate, protein or fat, the key is the number of calories expended. Exercising at the intensity the FBZ requires will take much longer to burn calories because the power output/energy requirement is so low.

EXCEPTIONS: Exercising in the zone may be useful however for severely deconditioned or obese individuals who do not have the physical capacities to perform a higher intensity-type exercise routine. If this is the case, the fat burning zone should be viewed as a step toward progression.

The key is to MAXIMIZE the number of calories expended

Unless you have many weeks and tons of patience to lose weight by consistently exercising in the FBZ; the best option is to maximize the number of calories burned in the shortest time frame. Interval based training is much better suited for quick and safe weight loss.

Basically interval training involves “bouts” of high intensity exercise separated by lower intensity “recovery” periods. An example of an interval might be running at high intensity (80 – 90% HR max) for 2 minutes and then walking (60-65% HR max) for about 4 minutes – keeping the work (run) to recovery ratio about 1:2 or 1:3.

The walking sessions serve two purposes: they contribute to total calories burned and allow for recovery and energy regeneration for the next successive running bout. This type of intermittent intensity training allows for a much greater burning of calories in a much shorter time frame speeding up weight and fat loss.

So even if I burn carbohydrates with higher intensity interval-type exercise I can still lose fat mass?


Remember the source of the calories does not matter. The carbohydrate stores in your liver and muscles (called glycogen) depleted from exercise must be replaced during recovery. So essentially more calories from food consumed after exercise will be directed toward glycogen restocking and less will be directed toward fat storage (it is only after the glycogen reserves have been restocked that the “excess” calories are directed to fat storage anyway).

Higher intensity exercise offers other benefits too

Research also shows that higher intensity exercise increases your post-exercise oxygen consumption (EPOC) and your post-prandial (after a meal) oxygen consumption. In other words, during recovery your metabolism is quite significantly increased for several minutes to hours after stopping exercise. This boosts your caloric expenditure even more over lower intensity FBZ-type exercise.

High intensity exercise will help you lose fat while sparing valuable muscle tissue and also promotes faster increases in your fitness levels since all your muscle fiber types (type I, type IIA, IIB) are stimulated in the process.

In conclusion then, this article has pointed to the importance of exercise intensity on the burning of calories. Clearly if your goal is to lose weight and fat mass faster and become fitter, interval based training is by far superior to exercising in the fat burning zone.

David Petersen is a Personal Trainer/Certified Strength and Conditioning Specialist and the owner and founder of Body Tuneup Shop Inc. based in Clearwater, Florida. More articles, information and client testimonial video clips can be found at http://bodytuneupshop.com

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Author: Piyawut Sutthiruk

Losing weight will keep you healthy and have a long life. Cheer Up!

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