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HIT And The Afterburn - Does it Really Speed Up Your metabolism and Boost Fat Loss?

If you're looking to boost your metabolism, you may have heard that high-intensity interval training (HIT) is the way to go. But is it really as effective for fat loss and firing up your metabolism as many people claim? In this post, we'll take a look at the evidence behind HIT and steady-state exercise, including what they are, how they affect metabolism, and which one may be best if you're looking to maximise fat loss.

What is the afternburn effect?

The afterburn effect, sometimes called Excess Post-exercise Oxygen Consumption (EPOC), is a term used to describe the increase in metabolism or number of calories burned after high intensity exercise. During an intense exercise session, your body uses up its stores of energy (namely glycogen) and fat to fuel your workout. Once you stop exercising, your metabolism continues to burn calories at an increased rate as your body works to restore is energy stores and return to its resting state.

Studies show that the intensity of the session relates to the how big this afterburn (EPOC) effect is. HIT sessions that involve pushing yourself to the max, show to have a larger afterburn effect than easier exercise, which makes sense.

But does the afterburn lead to fat loss?

This study compared a High intensity Interval workout (HIT) (4mins hard, 3mins easy), a Sprint Interval (SIT) (60s sprint, 4 mins easy) workout and Steady State Cardio (SSC) (30mins steady session).

The study showed that the afterburn for both interval sessions was around 100 calories, where the SSC session was around 60 calories. This extra 50 calories is not really going to have much of an impact on fat loss. To put it in perspective, 50 calories is around half a Freddo!

What's also interesting is that we know that the afterburn drops significantly after the first hour. So when you hear your favourite instagram celebrity claiming his HIT session will fire up your metabolism for 24hrs, he's wrong.

We also need to consider the amount of calories burned during the workout itself. As you can imagine, high-intensity workouts require more energy and burn more calories compared to less intense forms of exercise, however you won't be able to sustain this high intensity as long as an easy workout. So even though you might be able to burn more calories doing hard exercise, the rest periods and total length of the session will off set the total calorie burn. Which is highlighted in the same study. The SSC session burned 350 calories, the HIT session burned around 330 and the SIT session only burned 270 calories.

So in short, it's not necessarily a more time efficient way to burn more calories and the total calories burned when you include the afterburn, are probably pretty similar.

This isn't the only study either. A meta analysis which pools together results from a number of research papers, found that there was no significant difference in weight loss between SIT, HIT workouts and SSC.

So which is best?

1. In short it doesn't matter. Some people prefer the convenience of a steady session, while others like the short sharp spike of HIT workouts. So go with what you prefer.

2, Nutrition matters most. Exercise alone will do little for your weight loss goal if you haven't gotten control of your diet. If you're looking to lose fat, then the best way to lose weight is through better nutrition.

3. Don't feel you need to choose. If you really don't want to do HIT or SSC then don't feel like you have to. Providing you're adding in some sort of movement into your day, then you're doing ok! So go for a walk, take the stairs, play with the kids - whatever works for you. Just get moving! :)

Other things to consider

Do you want to get fitter? - If we look beyond just fat loss, High Intensity Interval Training is one of the most potent weapons in your arsenal to increase your VO2Max (cardiovascular fitness), and when combined with steady state (zone 2) cardio session it can have an even greater impact.

Fitness pays - I've performed hundreds of metabolism tests and anecdotally, fitter individuals tend to have faster metabolic rates. So it pays to do at least some sort of activity if you want to rev up your metabolism.

Like anything nutrition and exercise, when it comes to building the perfect fat loss plan, you need to consider how it interplays with your lifestyle . Are you short on time? Then HIT might be a good option for you. Do you prefer the consistency and convenience of steady state workouts? Are you focusing on strength? Then too much cardio may impact your progress. Are you in a large calorie deficit? Then HIT training might not be the best way to go..

There is no 'one-size-fits all' solution. So before jumping head first into any type of workout as the 'best' way to lose weight, you need to consider a holistic plan in line with your individual goals, schedule and your body.

If your goal is fat loss and struggling to find something that works for you. Then get in contact so we can show you how metabolic testing can help unlock your weight loss plateau.


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