sports nutrition

Fasted cardio, fat adaptation, why?

Talk of fasted cardio and fat adaptation is all the rage these days in fitness communities as diverse as CrossFit and the ultra endurance athletes set. Those are usually strange bed fellows (one says “too much cardio is pointless” and the other says “run all the miles”) so when something has caught both their attention it might be worth listening.

What’s fasted cardio? Basically exercising–running, biking, rowing, etc–first thing in the morning before eating.

Why do such a thing?

See Gretchen Reynolds, The Benefits of Exercising Before Breakfast

Exercising in a fasted state (usually possible only before breakfast), coaxes the body to burn a greater percentage of fat for fuel during vigorous exercise, instead of relying primarily on carbohydrates. When you burn fat, you obviously don’t store it in your muscles. In “our study, only the fasted group demonstrated beneficial metabolic adaptations, which eventually may enhance oxidative fatty acid turnover,” said Peter Hespel, Ph.D., a professor in the Research Center for Exercise and Health at Catholic University Leuven in Belgium and senior author of the study.

One warning: Some say that fasted cardio is as likely to use muscle for fuel as fat so while you’ll lose weight you won’t get any leaner. See Fasted Cardio Eats Muscle. There’s also the claim that you’re better off not fasting and doing a high intensity workout instead. See Is Fasted Cardio the Best for Burning Fat? There’s lots of skepticism out there. See AM Cardio Myth Exposed.

But for now let’s just set the worries to one side and continue.

The goal isn’t just to lose fat. It’s to change how your body works. You want to train your body to rely on fat stores for fuel rather than carbohydrates.

You want your body to become, as they say, fat adapted.  What does it mean to be fat adapted? Read this from Mark’s Daily Apple. You get the idea pretty quickly from the language. Sugar burners have it all wrong. Those who are fat adapted have got it right.

Okay, so my story. My past experience with fasted cardio isn’t great. Food is a real challenge for  me and morning exercise. In the past it’s been enough to stop me running in the morning even though that’s when it best fits my schedule. I wake up hungry and have to eat before exercise. But I can’t run on a full stomach so I have to set my alarm for early, early and then wait. I used to cycle with a young woman with the same issue. She used to set her alarm for 4 am, get up, eat breakfast and then go back to bed and nap til our 6 am ride.

I’ve tried to change my ways, really I have. I blogged about intermittent fasting and wrote, “A few years ago on the advice of a personal trainer I experimented with morning workouts on an empty stomach but that was a bit of a disaster. ….Halfway through my morning run I was prepared to go knock on doors in search of breakfast.”

I’m hungry a lot. It’s part of why intuitive eating hasn’t appealed to me as much as it has to Tracy. I’m hungry when I wake up and often I go to bed hungry. I don’t feel like there’s lots of non hungry eating to get rid of in my life. Weight loss for me has always involved hunger. I can manage it, make peace with it. Hunger isn’t an emergency. But I can’t exercise when I’m hungry.

I’m jealous of people who can get up and go. Many years ago when Tracy was two hours a day in the gym, in the morning, I once asked her what she had to eat first. She said she had a glass of orange juice.

That made me laugh. I was eating the full fruit and oatmeal breakfast and still needing 2nd breakfast after morning workouts. Morning swim workouts were worse yet for managing hunger.

But on the bike things are different for me. I can go a long while without eating if we’re not going fast. I have smaller friends–Hi Eaton! Hi Tracy!–who need to eat more often but I can do some pretty long rides without food. If I slept in and you showed up on my doorstep with your bike, ready to go, I’d be happy to leave the house with a banana and a Cliff bar in my pocket and eat on the bike. I can’t eat while running.

Cyclists vary about this. Me and another larger woman cyclist once sat watching in shock as we were eating poached eggs and english muffins as the some of the young men we’d been riding with were chowing down waffles, pancakes and french toast. How could they eat that much?

There’s two sides to this, good  and bad.  On the good side, they were eating like that because they can. On the bad side, they were eating like that because they had to. Our upside is that we can ride on very little food.

It’s hard for me to lose weight but on the bike I can ride without constantly refueling.

I’d never go without adequate carbs in a race. No, not ever. You’re slower, for sure. There’s lots of debate about high fat/low carb diets in the cycling community but all the evidence shows that when racing you’re faster if you’re consuming adequate carbohydrates. Your body can use other sources of fuel–i.e., fat and muscle–but it’s less efficient doing so. You slow down.

But training, why not?

Well, first. Why? Weight loss.

Second, the ability to go long distances with minimal fuel.

Women are better at this than men apparently. It’s part of the story, along with higher body fat stores, about what makes women better ultra endurance runners. The longer the distance the closer the gap between men and women and at the very long distances, women win.

But here’s my reason, which is neither of those, convenience.

I want to be able to run in the morning without setting a 5 am alarm. I want to run at 6 am so I can be home by 7 am to wake teenagers. (Yes, waking teenagers is a big thing in my life.)

So my experiment is to start by taking it easy. Go out there on an empty stomach and walk/run. This morning I even did walk one block, run one block. I didn’t get dizzy or woozy and I ate a normal breakfast after.

The plan is to increase gradually and see if I get used to it.

I’ll report back and let you know how it goes. Maybe one day I’ll be able to run run after a glass of OJ!

4 thoughts on “Fasted cardio, fat adaptation, why?

  1. My experience differs based on my type of training. On Saturday mornings I’ve been running up to 12 miles with no breakfast or even juice, with no issues at all. I use our group’s water stops to rehydrate. But for a race, or distance cycling, I have breakfast first. And I wouldn’t dare step on the Aikido mat unfueled. I found out what happens if I do, and it isn’t pretty. 🙂

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  2. Best of luck with your breakfast experimentation and “fasting”. Let us know.

    My body needs have a changed abit over the years. I used to just drink milk or tea for breakfast then cycle with a few hills to work…16 km. one way into downtown Toronto which had some minor stresses of traffic, etc. Same for returning home …maybe a muffin and tea for the entire work day. Yes. No lunch. This was every day in the summer for cycle-commuting in Toronto for a 32 km. round trip.

    Now for same distance today, I would need to have a small bowl of cereal with skim milk plus tea before setting off in morning.

    I agree poached eggs, English muffin and a juice would be a decent breakfast for a 50 km. long ride or so. Or maybe ….still too much for some folks. 🙂

    There are have been times I threw in an extra pancake or waffle. But was eternally grateful 3 hrs. later, while still on bike.

    The trick is not eating alot for dinner..unless one has a day long ride the next day. Rule: Eat 80% full..a traditional approach followed by the Japanese.

    Hungry is not the signal for me, but starting to feel depleted and need to stop for a few min. off bike for water (when I needed still something more to eat). I have come close to collapsing. So I’d rather eat properly for breakfast prior to a ride and ease off eating much for supper. I guess that defines for me, just eating less. Not “fasting”..somehow that suggests severe food/nutritional deprivation which is not what I want to do.

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  3. Generally I work out before breakfast….but I sometimes need to eat as soon as I wake up. I do sometimes worry that exercising on an empty stomach might have negative impacts on the body….but at the end of the day I just focus on getting the workout done whenever I can….

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