It has been an ongoing debate to which method of burning fat is brings faster total fat loss, some experts promote the fat burning zone which occurs during exercise and other experts promote the after burn which occurs after exercise. Both methods have its benefits and flaws but only one method has superior longer lasting benefits. This article dives into the science of fat a little more than usual to help you understand the benefits and flaws of both methods. Fat may seem like the enemy of civilized society but the fact is, we can’t live without fat. Fat plays a key role in the structure and flexibility of cell membranes and helps regulate the movement of substances through those membranes. Fat is also important in helping to regulate inflammation in the body and immune system function. Of course, the best-known functionality of fat is as an energy reserve.
Fat has more than twice the energy storage capacity at 9 calories per gram while carbohydrates and protein only have 4 calories per gram each. It has been estimated that the average lean adult male stores about 131,000 calories of fat, which is enough calories to keep a man alive for about 65 days. For weight loss enthusiasts the prime concern arises when the body’s fat storage functionality works a little too well, making people unhealthy and concerned with their outward appearance. When you have a better understanding of how fat travels through the body, you’ll be better equipped to reduce excess body fat and maintain an attractive physical appearance.
The Journey of a Fatty Acid to Muscle
Fat is stored primarily in fat storage cells called adipocytes. Most adipocytes reside just under the skin (subcutaneous) but they also reside around and protect vital organs (visceral). Most fat is stored in the form of a triglyceride. A triglyceride has a glycerol as its backbone with 3 fatty acid tails. If you were to look at a triglyceride under a microscope it would look like a camera tripod. Depending on the body’s energy supply or energy needs, adipocytes can either store fat from the blood stream or release fat back into the blood stream.
Right after you eat a meal, when energy supply is high, the hormone insulin is released which causes adipocytes to retain all their fatty acids. A few hours after eating or (especially) during exercise, epinephrine (adrenalin) is released. When epinephrine binds with adipocytes, their stored triglycerides go through a process called lipolysis, which causes fatty acid tails to be released from their glycerol backbone and the fatty acid and the glycerol can be released into the blood stream.
Fat does not dissolve easily in water, so once it enters the water-based environment of the blood, it binds with a carrier protein called albumin, which carries it to the muscles. Once fat enters the capillaries surrounding the muscles it can be released from the albumin and carried into the muscle. Once the fatty acid enters the muscle, a molecule called coenzyme A (CoA) binds with the fatty acid and prepares it for one of two fates. CoA is a carrier protein which maintains inward flow of fatty acids inside the muscle.
Two Fates of Fatty Acid inside Muscle
- Fatty acid oxidation takes place, in which an electron is removed from a molecule to produce energy.
- Fatty acid storage within the muscle.
Fatty acid oxidation is the fate for 80% of the fat that enters the muscle cells while the rest is stored as triglyceride droplets for later use. When fat is oxidized, it enters the mitochondria of the muscle’s cells where it undergoes a series of enzymatic pathways and finally converted to ATP (adenosine triphosphate) which is the directly usable currency of energy for muscle contraction.
At the beginning of exercise, more blood flows to adipose tissue causing more fatty acids to be entered into the blood stream. Exercise intensity has a direct impact on how much fatty acid is being converted to energy. We burn the most fat during low to moderate intensity bouts of exercise. When exercising at maximum intensity we burn a lower ratio of fatty acid compared to carbohydrates from glycogen, which is stored in muscles the liver. This is because less blood flows to adipose tissue and is being channeled directly to working muscles in order to keep up with higher oxygen demands. It’s very common to hear people talk about exercising at lower and moderate intensities instead of higher intensities to burn more body fat, which is known as the fat burning zone.
Benefits of EPOC
EPOC stands for excess post-exercise oxygen consumption, or fat burning that continues 24 to 48 hours after we have already stopped exercising. It’s also known in many fitness circles as the after-burn affect. EPOC is the number of calories your body burns after you finish exercising to return you to a point of homeostasis. More fat is burned during EPOC and EPOC is at its highest 30 minutes to an hour after intense exercise but can last for a total of 24 to 48 hours. HIIT, or high intensity interval training is a form of exercise designed to maximize the calorie burning effects of EPOC. Resistance training also results in elevated EPOC. For this reason, it is more beneficial to burn as many calories as possible during exercise and not overly focus on the type of calories being burned or the fat burning zone.
Calories lost will equal to fat loss, either during or after exercise. If less fat is being burned during exercise, more fat will be burned afterwards, and vice versa. When you exercise at high intensities, many training adaptations take place to help you burn more fat in the future. More carrier proteins become available which can deliver more fat to working muscles during the same amount of blood flow, more capillaries begin to form in muscles so that they’re able to consume more fatty acids and oxygen and triglyceride droplets stored in muscles become more efficient and readily available to deliver energy to working muscles. When your body becomes more efficient at burning fat, this means that you’re able to exercise even longer and harder with less fatigue and less recovery time, making it easier to burn more calories and lose more weight.
