Cardio and Fat Burning… O, that’s how it works

Many misconceptions exist over what method of cardiovascular training provides the most efficient and effective results for fat oxidation (energy consumed or extracted from fuel) or the more commonly referred term: fat burning.

Likely the greatest ongoing delusion is that cardio is the best method to burn fat, followed by erroneous belief that the faster you run the more fat you burn… wrong and wrong.

Before we get started, I feel it is important to point out that this article was created specifically to address the best methods of cardiovascular training for the purpose of burning fat, not improving athletic performance, endurance or oxygen utilization.

That being said, cardiovascular training is NOT the most effective method of exercise for burning fat. (In fact overdoing cardio may adversely slow your metabolism and lead to excess fat being stored). The most effective form of exercise to combat excess fat is resistance (anaerobic/weight) training. (Yes ladies… stop rotating between the treadmill, elliptical and steppers and instead head into the weight room… I promise, “You will not bulk up overnight into a she beast.” Unlike cardiovascular training, resistance training when performed properly is capable of preserving or increasing the amount of metabolic enhancing lean muscle tissue and contributing to a beautifully proportioned athletic shape. As far as running goes… only sprinting creates shape because it is anaerobic – all the long distance running in the world won’t build better glutes or thighs… in fact, over do it and the shapely muscle will waste away … not fat.

Regardless cardiovascular training remains very popular and is an important part of your lifestyle / exercise program.  The cardiovascular system is limited to your heart, veins and blood vessels including your lungs that circulate oxygenate blood and removes waste systematically. Cardio exercise is defined as any rhythmic activity that elevates the heart rate for periods greater than 20 minutes… yes-even sex can be considered a cardio workout… if you can pass the 20-minute threshold.

What is the most effective method for burning fat with cardiovascular training?

Points to Consider: Optimum time of day…how long…how often…and what of level intensity?

Time of Day:

The most effective time of day to perform cardiovascular training for optimum fat burning would be first thing upon waking and consuming your first meal (breakfast) following the cardio session.

How Long…How Fast…How Often:

As for duration, pace and frequency, the answer is plain and simple… slow, steady and sporadic wins the race. Maintaining a heart rate of approximately 65 – 70% % of maximum* capacity provides optimal fat burning potential. Typically 45 minutes to 1-hour sessions 2 to 3 times a week is sufficient. Sessions should be a minimum of 20 minutes to an absolute maximum of 75 minutes  (without taking in nutrients) and never more than 4 days a week when burning excess body fat is the goal.

Explanation:

Like any internal combustion engine, humans require a mixture of fuel and oxygen to perform a given task. The percentage of the fuel mixture (fat, carb or protein) is dependent upon pace or more accurately the oxygen consumption . Over time the stored fuel (fat, glycogen or muscle tissue) is depleted, We all burn some mixture or combination of fat, glycogen or protein the preferred source or greater percentage of fat being used as a fuel is dependent upon oxygen availability, dictated by the level of intensity.

Generally speaking, most of us have vast quantities of stored fat… enough to run a dozen marathons in a row.

What we don’t have is unlimited glycogen (stored carbohydrate in our muscle cells). The more muscle one has, the more glycogen, but the more muscle the more fuel is required to move the muscles.

It is for this reason that performing any heart raising cardiovascular activity for greater than 75 minutes may become counter productive (and why marathoners take in sugar based drinks during the race)… because the body has spent the limited glycogen stores and in order to provide the required percentage of glycogen, the body systematically starts breaking down muscle tissue (gluconogenesis) to continue fueling the motion.  Something you never want to do!

Muscle is a great metabolic booster so you want to protect the muscle tissue you have, loosing muscle mass will ultimately slow your metabolism. Understanding your body fat to lean muscle ration is of critical importance to gauge your success by periodically testing your body fat percentage and not the scale!

A FREE waist circumference body fat calculator to estimate your body fat percentage, describe healthy levels and illustrate your lean body mass total is available on the top right hand corner on the home page – www.unifiedlifestyle.com

Partaking in heart raising cardio activities beyond 20 minutes regardless of variety or type of cardio exercise should not exceed 4 sessions a week. Beyond that, your body may start adapting to the load being placed on it and send an anticipatory signal to slow the metabolism. Remember the human body has a genetic predisposition that has been programmed over the last 3 million years to store fat for times of famine.

Intensity:

Many people believe the faster they run, the faster they will lose fat…it may sound logical but it does not take into account how the body utilizes stored fuels…namely the macro nutrients Fat, Protein and Carbohydrates

It is important that the reader understand that we are talking about High Intensity Cardiovascular Training and not High Intensity Resistance (Weight) Training – these two types of exercise are diametrically opposed and the principles outlining the negative aspects of High Intensity Cardio on fat burning do not apply to High Intensity Resistance training. High Intensity resistance training is very beneficial for fat burning provided optimum rest periods between sets and muscle groups between training sessions are provided…thus the reason cardiovascular training is synonymous with aerobic training (with oxygen) and resistance or weight training is categorized as anaerobic (without oxygen) but that is another article.

A popular misconception is that High Intensity Cardiovascular Training (HICT) burns more calories in a shorter period of time and keeps the metabolism revved up post workout. The first problem in this statement is that the theory suggests HICT burns more calories…not fat. I cannot stress this point enough, CALORIES DO NOT EXIST! A Calorie is simply the name used to describe a unit of measure of energy, which is indiscriminate of the source of energy. In this case the topic of concern is fat oxidation not simply utilizing energy in a time efficient manner regardless of source of macronutrient namely carbohydrates, protein or fat.

Therefore I suggest that you pay no attention to the little gauge on the cardio machine that ticks away the number of calories used during the exercise increasing the rate of calories allegedly consumed the faster you go. The explanation is quite simple; fat requires more time and energy to digest than the other macronutrients and is also the most energy dense nutrient (which also explains the reason why the human body stores fat – simple economics of space. Imagine how large people could be if we stored carbohydrates with less than half the energy /caloric density of fat per gram) so too does this density apply to the oxidation or burning of fat through exercise. Slow and steady wins this race every time. As soon as you elevate your heart rate beyond the optimum 65% capacity – the body will convert from burning energy (calories) primarily from fat as a fuel to accessing energy from stored carbohydrates (glycogen) or protein (muscle).

The explanation is based on the simple fact that fat requires an oxygen rich environment to burn. When oxygen is not abundant – meaning when the heart rate is elevated to a level which creates a greater demand for oxygen to fuel the motion (faster pace = faster heat rate = more oxygen consumed) therefore as an economic measure the body will cease burning fat and commence accessing the more efficiently combustible fuel source of glycogen (carbohydrate) stores.

If one was to maintain a high heart rate pace and deplete all of the stored glucose the body will then access and commence burning the next most efficient fuel source which would be protein by breaking down muscle tissue – something you never want to do. This is the reason why you frequently see marathon athletes intake some form of high glycemic drink or snack at intervals during a race to replenish the fuel in attempt to spare muscle from being catabolized to provide fuel.

It is for this reason that I recommend exercise does not exceed 75 minutes in length as the glycogen fuel sources are typically depleted and the body will then be left with no alternative but to commence breaking down protein (muscle).

What About Walking:

Walking does not typically raise heart rate substantially and can be performed for long periods because the dominant fuel in the mixture is fat. Fat burns efficiently in an oxygen rich (low heart rate) environment.

Moral of the story – Walk you dog everyday… even if you don’t have one.

* To determine an individual’s maximum capacity heart rate a simplistic and widely accepted formula is 220 beats per minute – minus your age. E.g. 220 – (age) = max heart rate – Multiply this number by 65% to determine target heart rate.

Scientific Support:

An Intensity Study on Fuel Utilized through endurance orientated exercise (cardio)

Comparison of various exercise intensities on plasma glucose (blood sugar) concentrations after 30 minutes of cycling found that as intensity increased, plasma glucose concentration increased. Specifically, the mean values were 77, 98, and 147 milligrams per deciliter of plasma glucose concentrations for 25, 65, and 85 % V02 max intensities.

This facilitated a higher reliance on glucose, as carbohydrate utilization increased as intensity increased. In the 25 % V02 max condition, carbohydrate oxidation provided approximately 7.5 % of the fuel used. Further, muscle glycogen stores did not contribute significantly to this number, suggesting almost complete reliance on peripheral glucose.

In the 65 % condition, carbohydrate utilization provided approximately 50 % of the fuel utilized, with 80 % of this coming from intramuscular glycogen stores.

During the 85 % V02 max condition, 75 % of the energy was derived from carbohydrate utilization, with 80 % coming from muscle glycogen stores.

The proportion of fat oxidation, showed an inverse relationship with exercise intensity. Over 85 % of the fuel during 25 % V02 max was provided by fatty acids from adipose, while 7.5 % was provided by intramuscular TGs (triglycerides). In the 65 % condition, 50 % of the fuel was derived from lipid (fat) oxidation, in equal measure from adipose and intramuscular stores. The lowest percentage was found in the 85 % condition, with only 25 % of the fuel coming from lipid oxidation from equal measure of adipose and intramuscular TGs

From the above findings it should be noted that total fat oxidation is greatest at moderate intensity, while total glycogen depletion is greatest at high intensity exercise. Fat utilized from adipose tissue was greatest in the low intensity condition, while glycogen depletion was lowest at this intensity.

This suggests, that based on lipid oxidation, that 65 % V02 max is optimal.

© 2011 Copyrights Grant Roberts, All Rights Reserved