Fit and Fasted: Is Exercising on an Empty Stomach Better for Us?

Fasted Exercise


Exercising on an empty stomach sounds counterintuitive. Food is fuel, so can we workout effectively if we’re running on empty?

Our relationship with food is complicated.  The information we’re given about what’s good and what’s isn’t is often contradictory.  Opinions on what’s best for our bodies and general health can turn faster than a tide, and it’s hard to know what’s best.

Fasting before exercise has generated a lot of mixed opinions.  Science says it’s an ideal state to workout in.  Science also says that it’s not.

Google it.  Go on, we’ll wait.

Confusing, right?

People have fasted for centuries.  Some religions still insist on it. People fast for inspiration, for enlightenment and now for diet and fitness.

I know that fasting worked for me when I needed help reassessing my relationship with food; it helped me reset some of the questionable eating habits that I’d formed over the years.  The weight came off slowly and it’s stayed off, and it was liberating to feel hunger rather than feed it.  In the West, we seem to equate hunger with starvation but the truth is that putting our bodies in a fasted state can help us make better food choices. It can make us more focused, too.


Fasted Exercise


What about fasting for exercise?

I used to run in a fasted state, too.  It wasn’t a deliberate choice. It’s just that I liked to go in the early morning when everyone else was asleep and everywhere was peaceful and I could bounce along without an audience.  I never thought about the fact that I hadn’t eaten. I wasn’t thinking about glycogen levels or if I was burning muscle instead of fat.  I trained for a half-marathon like this.

When I see articles saying that fasted cardio doesn’t work I am a little sceptical.  It’s worked for me. But the body is complicated.  It’s not unreasonable to think that there’s a place for fasted exercise but that it isn’t for every regime or for everybody. Health isn’t straightforward and good fitness sometimes straddles that line between what’s very good for us and what could be harmful. Fasting might not have worked as well for me say, for instance, I was looking to increase my muscle mass.  It might also not have been the greatest idea if I’d had a history of eating disorders.

Many of us choose to workout first thing. Metabolism is better in the morning. If you’re an early riser and on a tight schedule, then you may not have the time to wait for your breakfast to digest.  It makes sense to get up, get out and get going. You may already do this without really thinking about it.

We’ve had a look on the internet (of all places) to see if we can figure out whether you can get fit fasted.

What is fasting?

For some, fasting means no food before exercise. This might mean jumping right out of bed in the morning and heading out to the gym or for a run.  For some, fasting can just mean avoiding carbohydrates so eating a small protein based breakfast can still be classed as fasting. By this definition, it means that if you use coffee to help smash your workout, then you don’t have to give it up in order to fast effectively.

Does Fasting Help with Fitness?

Proponents of fasting before exercise say that it helps you to burn fat quicker. They’re not wrong. The body stores excess glucose in the liver where it becomes glycogen and during exercise, the body uses this glycogen as fuel to keep us going.  In the morning, our glycogen reserves are pretty low,  so when we exercise first-thing without eating, they can hit empty pretty quickly and this is when the body is forced to start burning fat.

Hooray! Yes?


Studies do suggest that you’ll shed more fat doing cardio in a fasted state.  Time has written about one 2013 study where 64 obese adults fasted every other day an followed an aerobic programme.  The results? They lost more weight than if they’d exercised or dieted without fasting. Other studies have supported the same idea, too.

The problem is that once it’s run out of glycogen to burn, your body isn’t just interested in burning fat but protein, too.  It can also start breaking down muscle. This is probably the last thing you’ll want to happen if you’re strength training.

Strength and Conditioning Journal, describe one study showing that whilst fasted and non-fasted cyclists burned the same amount of calories in the experiment, those who’d fasted actually lost 10 % of their calorie burn from muscle.

Another problem is that low glycogen can affect our energy levels, too, making exercise feel tougher than it is.  One thing that we really don’t want to do is make things harder for ourselves.  Without sufficient energy, it’s going to be much harder to smash targets. This could have an impact on overall calorie burn and on motivation.  It could mean that our efforts plateau.

Greatist, however, thinks fasting is pretty awesome, and they’ve got Hugh Jackman as their poster boy on this.  He used intermittent fasting to get into shape for one of the Wolverine films and honestly, does the man look like he’s suffering from a loss of muscle mass?

The website goes on to point out that fasting increases traces of a growth hormone by 2,000 percent and in women by 1,300.  This hormone helps burn fat, build new muscle tissue and improve bone quality.  The effects of this hormone end once you’ve broken your fast, so they encourage regular fasting to maximise its benefits.

Fasting can also help to lower insulin levels which is great news if you’re diet has put you at risk of diabetes.


Fasting Before Exercise or Breakfast


The T-Nation website, however, isn’t convinced that cardio in a fasted state works as well as others have suggested.  For them, it’s all about the cortisol: the energy spike that gets us up and out of bed in the morning.  Cortisol stays elevated in the body until you eat so by skipping food and going straight to cardio, it’s going to get higher and higher and that’s another way that muscle can start breaking down.

There’s an argument, too, that your metabolic rate will drop after your body starts burning fat and that the next time you eat it’ll store more fat to compensate.  Lifehacker argues that this renders any fat loss gained through fasting pointless and that the benefits are only short-term when compared to working out in a non-fasted state.

There has been one Belgian study, however, that did post some interesting results. They split adult males into three groups: the first group ate a diet that was very calorie and fat heavy and were told not to exercise.  The second group had the same diet but followed an intense exercise regime that included eating breakfast before exercise.  The third group ate the same number of calories as both groups and followed the same exercise regimen as group two but group three didn’t eat breakfast before working out and only drank water during. They caught up on the calorie intake, however, once they’d finished working out.  

  • Unsurprisingly, the first group put on weight.

  • The second group did, too, although not as much and both groups became more insulin resistant, too.  

  • The third group who’d fasted barely put any weight on and showed no sign of insulin resistance.

That’s pretty interesting.  Given that the only real difference between group two and three was that the latter exercised in a fasted state.

The NY Times published what the authors of the study said “Our current data,” the study’s authors wrote, “indicate that exercise training in the fasted state is more effective than exercise in the carbohydrate-fed state to stimulate glucose tolerance despite a hypercaloric high-fat diet.”

No doubt this will become a rich topic for future studies, and we’d love to know what you think.  

However, you’re choosing to exercise remember your EarHugz if you're working out in headphones. Ear Hugs are sweat-resistant headphone covers that protect against sweat damage in the gym. 


Ear Hugs Sweat Resistant Headphone Covers





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