What is metabolic efficiency for runners?

For the last six months or so, I have been slowly tweaking my diet to become more metabolically efficient as a runner.  I’ve been reading articles, books and looking into the training to become certified to train others (is it worth a trip to Colorado? I’m thinking it might be!)

I’m going to put this content into a webinar soon but also wanted to share an overview as many of you have been asking about it.

Basically, metabolic efficiency is controlling blood sugar with nutrition (and smart training) to allow the body to become better at burning fat and using it for fuel.  When blood sugar is high, the pancreas releases insulin to reduce blood sugar which halts the body’s ability to use fat as fuel.

Metabolic efficiency is important both from a health perspective (managing or preventing diabetes and other nutrition related illnesses) and from an athletic performance perspective.

It’s really as simple as this: you burn what you eat.  When your diet is 70-80% carbohydrates and low fat (as the traditional recommendations for runners encourage) your body will burn carbohydrates for fuel.

When your diet is balanced between protein, carbohydrates and fat, your body will be able to use fat as fuel and less carbohydrate stores.

Why is this important?

Did you know that the body has about 1500-2000 stored carbohydrate calories at any time? When you use those up in a long endurance event like a marathon without adding more sugars/carbs to the mix, you hit the wall and bonk.

In contrast, any idea how many calories of fat our bodies have stored?

Up to 80,000 calories!! Even a lean athlete has about 50,000 stored fat calories available to use.

So teaching our body to use fat as fuel (arguably the better choice) we can avoid bonking, need less fuel for long runs and races, and therefore also have less digestive issues trying to process all of those gus and gels and sports drinks on the run.

Besides running better on less, it can help improve body composition as the body will be less in need of storing carbohydrates as fat, which can often happen for endurance athletes who find their body’s changing in an undesirable way as the miles creep up.

How do you become more metabolically efficient?

I’ll look at this in more detail in follow up posts, but the basic ideas is through a combination of fat burning (low heart-rate aerobic) exercise and nutrition that stabilizes blood sugar.  Nutrition makes up about 70% of that equation.

How do you know if you are burning fat on your runs?

There is a metabolic efficiency test that can measure your “crossover point” – generally you will burn more fat at lower intensities and as the intensity increases your body will switch over to burning a greater percentage of carbohydrates.

You want to do a good amount of training at the lower, fat-burning level (some use heart rate based training for this) to slowly push that efficiency point further along.

You don’t have to be tested to begin to help your body make this shift with nutrition and/or exercise.

I’m incorporating a lot of this info into sessions with my private nutrition and running clients who are interested.  I find it fascinating, and it’s definitely made a difference for me in performance, fueling and adding muscle/losing fat.

Have you looked into metabolic efficiency?

Do you have any idea at what point your body switches from fat burning to sugar burning?


32 thoughts on “What is metabolic efficiency for runners?

  1. I’m definitely interested in learning more about this as I contemplate getting back into training. I’ve read a bit about it and have made some tweaks and have seen the gains.
    Angela @ Happy Fit Mama recently posted..LatelyMy Profile

  2. As I work my way towards longer and longer races, this is something I NEED to learn more about and incorporate in my training and racing. My last 24 hour race I utterly fell apart around 14 hours/50 ish miles in. It was 100% because of nutrition. I think if I became more metabolically efficient in running, I wouldn’t need to shovel *as much* food in my face over those longer distances, with fear of bonking!
    RFC recently posted..Cankles & Keeping it Real.My Profile

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