Stop training on an empty stomach if you're a night owl

“Is training on a fasted stomach wise?” This is a question I sometimes get from my clients. And my answer? That depends on whether you are a morning person or an evening person, and what kind of training you do.

As a sports nutrition coach and an early bird, I've experimented with this myself. But not everything that works for me will work for you. Let me explain why.

An early bird is someone who naturally wakes up early and is most alert and productive in the morning. A night owl is someone who naturally tends to stay up late and is most alert and productive in the evening or at night.

In my practice, I see two types of people. Those who get up early and can get straight to work. And those who only start functioning after their coffee (and another coffee).

Morning people, also known as ‘larks’, wake up on their own early and are most energetic in the morning. Their energy dips around midday and in the evening. I am one of those morning people. Getting up early is not a problem.

Night owls, also known as ‘owls’, have the opposite rhythm. They have difficulty waking up early and only get going later in the day. Their best time is in the afternoon to evening.

Around 60% of people are morning people, 30% are evening people, and the rest fall somewhere in between. This difference also determines how your body reacts to exercising on an empty stomach.

What does exercising on an empty stomach do to your body?

When you wake up in the morning, your body has had no food since your evening meal. Your carbohydrate stores are almost depleted. Normally, your body uses carbohydrates as fuel first when exercising, but on an empty stomach, it has to switch to fat.

People who exercise on an empty stomach in the morning burn 20% more fat during their workout than those who eat breakfast first. That sounds great for anyone wanting to lose weight. But here’s the catch: this only works in the morning after a night’s fast. If you exercise on an empty stomach in the afternoon or evening, this effect doesn’t occur. Your body is no longer in that special ’fasting mode’ and has already taken in energy during the day. Research from Japan clearly demonstrated this. (Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC4703705/)

So, do you want to train sober for fat burning? Then it really needs to be in the morning, not later in the day.

The big difference: morning person versus night owl

This is where it gets interesting. Because even exercising on an empty stomach in the morning doesn't work the same for everyone.

As a morning person, your body is alert and ready for action in the morning. You feel energetic, even without breakfast, and can easily sustain light exercise.

For night owls, it’s a completely different story. Their bodies aren’t ’awake‘ yet in the morning; they feel weak and tired, and their performance is much lower. A study confirms this: night owls who have to perform early in the morning score up to 9% lower than they do in the evening. (Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC7098792/)

What do you need to do? My advice

As a morning person

You have more possibilities in the morning.

For light training such as walking, gentle jogging or cycling, you can train on an empty stomach. With this gentle exertion, your body can burn fat as fuel. While this is slower than burning carbohydrates, the energy demand is low enough to make it possible.

For intensive training or strength training, I recommend having breakfast first. During strenuous exercise, your body needs a lot of energy from carbohydrates quickly. Without those carbohydrates, your performance will suffer. You can't perform at your best on an empty tank. I've noticed this myself: as a morning person, I'm alert in the morning, but for a good training session, I always eat first. My go-to breakfast is porridge with blueberries. Other good options are two slices of wholemeal bread with peanut butter, or yoghurt with a banana and granola. If you can choose your training time yourself, train around 10-11 am for your best performance.

If you train in the evening after work at 7 PM or 8 PM, make sure you eat enough during the day and, if necessary, have a light snack an hour and a half before your training session.

As a night owl

Preferably train in the afternoon or early evening, when your body is at its best. Always eat something before your workout.

If you have no choice and have to train in the morning, accept that you won't perform at your peak and always eat something first. Your body needs that fuel extra badly. View it as maintenance training. Save intensive training sessions for later in the day if possible.

For everyone

Experiment and listen to your body. Do you feel dizzy or weak? Then eat something. The most important thing is that you exercise regularly and keep it up.

It's not just about fat burning

Yes, exercising on an empty stomach burns more fat during your workout. But that doesn't automatically mean you'll lose more weight. Exercising on an empty stomach often means training less intensely because you have less energy. This might lead you to burn fewer calories overall. Additionally, eating before training aids muscle recovery, and more muscle means a faster metabolism.

What is the most important thing? That you exercise at all. Research is crystal clear on this: regular exercise is far more important for your health than whether you exercise on an empty stomach or not. So, if the thought of exercising on an empty stomach puts you off, just have breakfast first. The best training is the training you actually do. (Source: https://theconversation.com/does-fasted-cardio-help-you-lose-weight-heres-the-science-264368)

My conclusion

Is training on a fasted stomach sensible? The answer is: sometimes yes, sometimes no.

For early risers, it can be done with light cardio, but not with intensive training. For night owls, it’s not a good idea in the morning. It’s better to train later in the day.

And remember: the best approach is one that you feel good about and can stick with.