How to Lose Fat with HIIT

The Afterburn Effect

You have probably heard of HIIT, otherwise known as High Intensity Interval Training, a method many people are using to lose weight fast. It’s proven that HIIT burns more calories in half the time than traditional cardio exercise.

It’s definitely efficient, but most people don’t know that some of those calories are actually being burned after your workout! In this article will teach you how you can keep feeling the burn, even after your workout is done!

HIIT is mostly explained in the name, it’s high intensity training with intervals of work and rest. This can be used in both cardio and strength training, examples being 30 seconds of sprinting with 60 seconds of walking/jogging, or a HIIT style Tabata, with 20 seconds of exercise and 10 seconds of rest. A full tabata lasts about 4 minutes, 8 rounds of that 20/10 interval that is usually split up into 4 different exercises.

HIIT is usually a type of anaerobic exercise, compared to traditional cardio, which is usually aerobic. Aerobic metabolism uses oxygen to turn your food storage fuel (carbs and fat) into energy for the body to use during exercise.

When the exercise becomes intense, your body’s oxygen supply cannot keep up with the demand of your tissues so it switches to mainly anaerobic metabolism, which doesn’t require oxygen to create that same energy.

The downside to anaerobic metabolism is that lactic acid is produced, so the exercise doesn’t usually last long before it builds up and you’re forced to rest while it clears from the tissues.

When scientists measured the calories burned from a high intensity work outs, they noticed something strange. Many of the added calories burned from anaerobic workouts happened after the workout and on the short breaks during intervals. The longer and more intense the training was, the longer this ‘after burn’ effect seemed to go on after the workout was done.

The key to why this happens is energy expenditure, which is a fancy way of saying the cost to exchange fuel like carbohydrates or fat to energy. Aerobic metabolism uses oxygen as a currency for this exchange. Anaerobic, however, cannot use oxygen and builds up an ‘oxygen debt’.

Since anaerobic burns way more calories and generally causes more molecular damage, that energy also costs more. Anaerobic metabolism essentially takes the energy you need in that moment and then pays for it later, with interest.

This is called EPOC: Exercise Post-Oxygen Consumption. As mentioned, anaerobic generally causes more damage and burns a lot of energy, so it requires a lot more recovery and repair time. The whole time you’re recovering your metabolism is being boosted to burn more fuel in order to ‘pay off’ that debt.

Since it’s using oxygen, it’s aerobic metabolism, which tends to burn fat as a main fuel compared to anaerobic, which uses carbohydrates. Aerobic can burn carbohydrates, but during recovery the body is focused on replenishing those carbohydrate and short term energy stores used during the workout, so fat is the primary fuel source burned.

The best thing? These ‘after burn’ effects can last anywhere from 16-38 hours.

Here’s a HIIT workout you should try:

If you want something that torches more calories in half the time both in and out of the gym, try some HIIT.

Here’s what we covered in this article:

  • HIIT is High Intensity Interval Training.
  • HIIT is a type of anaerobic exercise, compared to traditional cardio which is aerobic.
  • Aerobic metabolism uses oxygen to exchange fuel for energy.
  • Anaerobic does not use oxygen, which makes the energy more ‘expensive’, and creates and ‘oxygen debt’.
  • This debt is repaid by Exercise Post-Oxygen Consumption (EPOC) which burns fat during recovery while carbohydrates restock short term energy.
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Bachelor of Science in Nutrition and Nutraceuticals. A Canadian with a love of food, fitness and health.

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