What if I told you there was a way to burn fat, while sitting on your couch. Using science and an investment of effort, you can lose that gut DAYS AFTER YOU EXERCISE. The concept excess post-exercise oxygen consumption or EPOC, is defined as calorie burn even after you have completed your high intensity interval training (HIIT) exercise. This week at Maximal Being we Look at 4 Ways to Harness the Fat Burning Power of EPOC!
In a prior post debunking the myth behind starving yourself for fat loss, we described several concepts around energy balance in the body (HERE). Additionally, on our post on NEAT (non-exercise activity thermogenesis), we break down basal metabolic rate (BMR), a basic metric of your body’s ability to burn fat. Building further on this concept is a factor termed VO2 max or the maximal oxygen consumption.
VO2 Max the Measurement of Fitness and Values
VO2 max is the rate at which oxygen is used by the body during an activity. Note that your body delivers oxygen to the tissues (heart, lung, muscle, brain) via the red blood cells to perform action. Per the American Heart Association (AHA), VO2 max is an excellent measure of one’s physical fitness and rises with athleticism.
We measure VO2 max most accurately using one’s heart rate, heart rate variability and using a face mask which measured oxygen in and expired CO2. Usually what is spit out is a value in mL/kg x min. “Good” values:
- man are around 42-46 mL/kg.min
- woman 33-36 mL/kg.min.
Along the same lines a sedentary person will usually have a VO2 max around 27-30 for women and 35-40 for men.
When VO2 max is measured, typically, the values will form a curve. This curve can be measured during the time of the activity in question and a second curve can be created during the rest period which looks like the below graphic. The change in the VO2 max levels or area under the curve is EPOC.
The Purpose of EPOC is to Return to Baseline
As EPOC is the change between exertional VO2 max and resting VO2 max, it is a numerical example of your ability to return your body back to its resting state. During this time, several important processes happen, that allow your body to function properly, recover and gear up for the next exercise. Such factors include:
- Hormonal Balance
- Cellular Repair
- Replenish Fuel Storage (ATP and creatine)
Just to briefly side track anabolism is the process by which your body can take simple molecules (protein) into complex molecules (muscle). Also by fuel storage we mean adenosine triphosphate (ATP) and creatine. Your body takes these adenosine molecules with 2 phosphorous on it, breaks the bond, which releases a puff of energy.
To put the phosphorous back, your body uses phosphocreatine and loans a P back to the adenosine and the process cycles over and over.
The Two Fat Burning Phases of EPOC
Understanding that, let’s jump back to EPOC. During the immediate or alacticacidosis phase of EPOC you body performed this function, replenishing your ATP. During the lactic acid or delayed phase to follow, your body uses lactic acid to gain more efficiency at performing the functions above to get your heart rate, blood pressure, temperature and repair systems back to their initial state.
In order to get back to baseline, your body needs fuel. Glycogen (branched carbs) can assist, however your body also will release your fat stores into the blood in the form of free fatty acids, which can help with this delicate homeostatic process. Hence, EPOC, causes fat burning, but for how long.
Quality clinical research has shown that EPOC can last up to 38-48 hours after the initial exercise event. What is means is that you will burn fat for hours after your exercise. Even when the activity itself has stopped. The next question is, how can that time investment be most efficiently utilized?
HIIT is the Most Efficient Way to Burn Fat with EPOC!
To answer this question a landmark paper out of Purdue in 1992 showed that HIIT generates MORE EPOC when compared with aerobic exercise at a similar energy output. This has been followed with several studies in 1994 by Tremblay showing higher EPOC and beta-oxidation(fatty acid release) for HIIT versus endurance (long distance) effort, and Baker in 1998 with intervals as BEST again.
It appears that the interval component is most important, because a 2020 study showed that sprint intervals and HIIT both outperformed “moderate continuous exercise.” Though also noted is that weightlifting also has a large EPOC output as well. However, let’s be real, ANY exertion is better than NO exertion (NEAT right). This is just the best bang for your buck.
Harness the Fat Burning Power of EPOC Summary
EPOC is a period after exercise in which your body regulates and returns to steady state. During this time, you body can break down your fat and use fatty acids to help you recover. EPOC lasts for 38-48 hours even after your exercise, meaning YOU BURN FAT FOR DAYS without ANY change in exertion. Though any exertion is GREAT, use your valuable time efficiently by HIIT and weightlifting to, harness the fat burning power of EPOC!
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