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Are You a Fat Burner or a Sugar Burner?

When you exercise, of course you burn calories. But what type are you burning? Sugar? Fat? We tapped a sports nutritionist to find out the difference.

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fat burner vs sugar burner, woman running in sports braphoto credit: shutterstock

What’s your workout personality? Fat burner or sugar burner

Navigating the world of wellness can be a daunting journey. We’re constantly inundated with new information and fads and trying to wade through it all is often easier said than done. When we heard that you could be a sugar burner over a fat burner (or vice versa), I knew I had to dig a little deeper to find out what this means – and whether it’s something that matters in our day-to-day lives. We spoke with Nanci Guest, a sports dietitian and CLIF Bar ambassador, who broke down the sugar versus fat debate – and explained whether it even makes a difference.
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fat burner vs sugar burner, sugar as energy, sugar cubesphoto credit: shutterstock

Fat burner vs. sugar burner energy sources

photo credit: shutterstock

First thing’s first, “The sugar we’re talking about is carbohydrates, which is your body’s currency,” says Guest, explaining that most people confuse carbohydrates (which are broken down to glucose) with the sugar you’d find in sweets and fat in foods with the fat cells on your body.

To test out whether you’re a fat burner or a sugar burner, researchers “put someone through an exercise test, which measures the gas exchange rigged with a mask and breathing tubes, to precisely measure their gas exchange.” That helps determine how much carbon dioxide you’re producing versus how much oxygen you’re taking in. “Based on the respiratory quotient—the rate of carbon dioxide produced versus oxygen consumed has a range value of 0.7 to 1  – if the number is closer to one, you’re burning more carbohydrates than fat,” says Guest.

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Are you what you eat?

Just because you could technically get this test done, Guest isn’t convinced it’s necessary if you’re not an elite athlete focusing on endurance or trying to manipulate your calories, especially because a lot of this fat burner versus sugar burner business is dependent on your diet.

“If I’m on a high-fat, low-carb diet, my body is going to start utilizing fat as an energy source, because that’s what I’m taking in,” she says.  This shows your temporary fuel source. “Now moving up a gear or two as in easy cardio to faster running, cycling a hill, doing a circuit of weights – think breathing hard and high heart rate – requires carbohydrate as a fuel source. But don’t worry if you work hard, this does come off your body as fa. Fat simply does not have enough time nor the constant oxygen supply to break down fast enough at higher intensities of work.”

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Fat burner vs. sugar burner, so which is better?

In a perfect world, both.

Guest breaks down the numbers, saying: “If I’m window shopping or going for an easy walk, about 40 per cent of my energy comes from fat. If I break into a jog, about 30 per cent comes from fat. If I start running at a good pace, you use about 98 per cent carbohydrates and two per cent fat.”

She reiterates the fact that while you do use fat for some exercises (though they are leisurely), “there isn’t any workout where you can burn 100 per cent fat; your ability to burn fat is about zero to 40 per cent at most.”

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Being a fat burner does not equal losing body fat

“Where this all becomes a moot point is that whatever you’re burning during an exercise session is very poorly correlated with losing body fat,” says Guest. “I’ll lose a lot more [body] fat if I spend an hour sprinting 100 metres [about 500 calories burned], resting for a minute and repeating that, as opposed to walking at a moderate pace for an hour [about 300 calories burned]. I technically used more fat as fuel fat, by percent, during my walk.”

Guest says what we “want” is metabolic efficiency – switching between burning fat and sugar. And she adds: “Extreme diets, especially low-carb [diets], can hinder your ability to make these switches and can hinder your power. Your body gets less efficient at burning carbs, and carb breaking down enzymes get downregulated, which are needed for high-intensity exercise. Imagine that you have lots of fuel in the tank but your muscles can’t get to it because they forgot how to use it since you’ve been avoiding carbs so religiously.”

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It’s all in the twitchy fibres

“People often think, ‘why would I use carbs as a fuel when I have 80,000 calories of fat lying on my body,’ but the simple answer is that your fast twitch fibres require carbohydrates,” Guest explains. Fast twitch fibres are the muscle fibres that allow you to do powerful exercises – anything in the running, cycling, HIIT realm – while your slow twitch fibres are going to be your “longer endurance, more aerobic workouts.” Guest adds, “Your fast twitch fibres physically cannot use fat – they just don’t have it in their cells.” Which leads us to…

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“Carbs are not the enemy!”

People get this misconception that carbs are the enemy, but if you’re planning on doing any kind of workout beyond a leisurely stroll, they’re a necessity. The caveat to this is that “your muscles don’t recognize if that glucose is broken down from an organic apple, a slice of whole wheat bread or a piece of licorice.” The reason healthy carbs are recommended is because they also come with a whole other host of nutrients. It may be tempting to reach for a cookie before exercising, but that’s better reserved for a post-workout treat instead.

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Calories in, calories out

While counting calories can be a slippery slope for some people, Guest explains that weight loss is a numbers game and, for the average person, isn’t wholly dependent on whether you’re classified as a sugar burner or fat burner. “If your daily caloric requirement is 2,000 and you lower that to 1,800 and do an exercise that burns 600 calories everyday, you’re going to be in a caloric deficit and your body will start tapping into its fat stores.” Of course, your 600-calorie workout is going to be much more effective if you’ve fed your body healthy carbs, too.

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Digestion plays a part

“Eating high-fat foods before any workout (big or small) is never recommended,” says Guest, adding, “It can take up to five hours to digest high-fat foods, so your blood will be going to your gut to digest the fat,” instead of going to the muscles where you need it most during exercise. With that being said, some carbs aren’t good before working out either. “If you have an apple an hour before a workout, because it’s also high in fibre, it’s going to take 75 to 90 minutes to digest and enter your blood stream, whereas a banana can take seven to eight minutes.”

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Fuel for fitness

Now that we’ve all agreed that carbs are our friends (and we can stop naysaying them), what do you consume before or during a high intensity workout? Water, for starters, but beyond that, “If I’m in the middle of a run or spin class, I don’t want to be using any of my blood to start digesting food, I want all of it in my legs so I can crush my class,” says Guest as we enthusiastically nodded our heads in agreement.

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Should you get tested? (And does it even matter?)

The simple test is based on your heart rate: If your heart rate is considered low, even when you exercise, you may be a fat burner. And the opposite is the case if you’re a sugar burner. But that’s not the most accurate way to measure.

If you’re past the average healthy person point and are teetering (or fully embracing) elite athleticism, Guest suggests looking into executive health centres and universities who are executing tests and research of this variety, though it isn’t a standard test as of right now and she’s not sure it’s totally necessary for the day-to-day.

“We’ve come full circle and we’re inundated with so much data. Just because you can get this test, should you? Is it helping you with your health and fitness goals or is it overwhelming?” It’s really up to you.