Getting your foot out the door is winning half the battle in exercise. But once you’ve started working out consistently, you’re faced with more nuanced decisions. One of these is whether or not to work out on an empty stomach, also known as fasted exercise. Fasted exercise is growing in popularity, as more bloggers and fitness professionals extol its benefits. But not everyone is a fan of the idea — and with good reason. There are pros and cons to exercising on an empty stomach, but ultimately like most things to do with your health, it comes down to personal fitness, goals, and lifestyle. In this article, we’ll take a look at the pros and cons of fasted exercise, so you can make an informed decision about whether it is right for you.
Why You Might End Up Working Out On An Empty Stomach
First things first, what is fasted exercise? Simply put, it’s working out in a fasting state — meaning you haven’t eaten for several hours. This is different from working out after having a meal or snack, which some people refer to as “fed” exercise.
Note that for it to count as fasted exercise, you’ll need to go at least 8-12 hours without eating beforehand. This means that if your last meal was at 7pm, and you wake up to go for a run at 7am, that qualifies as fasted exercise.
Working out 3-4 hours after you’ve eaten, however, doesn’t count as fasted exercise. So if your last meal was at 1pm and you hit the gym at 4pm, that’s “fed” exercise — not fasted.
People who exercise in the morning or late at night often don’t have time for a snack or meal ahead of time — so fasted exercise can feel like the only option. There are a few other reasons why you may find yourself working out when hungry:
- For perceived weight loss benefits – a popular reason for doing fasted exercise is that it gives you an extra edge when trying to lose weight.
- Because you have no appetite when you wake up – depending on how early you wake up, you might not be hungry when you first get up.
- To give your digestive system a rest – fasted exercise is said to help give the digestive system a break, allowing it to rest and repair.
Working Out On An Empty Stomach Pros And Cons
What does the research say about fasted exercise? The truth is, there isn’t a great deal of scientific literature on the subject — and the studies that have been conducted yield mixed results.
Let’s take a look at the pros and cons of working out on an empty stomach, based on the available evidence.
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Working Out On An Empty Stomach – Pros
Below are some reasons why you might benefit from fasted exercise:
You’ll Burn More Fat
A study among 12 men found that when they exercised in a fasted state, they burned significantly more fat than those who had recently eaten (4).
Here’s how it works – when you’re in a fasted state, your body has no carbs to use for energy. This forces it to tap into fat stores instead – and that means you could be burning a great deal more fat than if you were exercising after having a meal.
For people with a lot of weight to lose, this could be an effective way to accelerate results.
You Might Eat Less Later
The same study involving men showed that those who worked out in a fasted state ate significantly less throughout the day than those who had eaten before exercising (4). If you struggle to control your appetite, this could be a great way to keep your diet in check.
You’ll Stave Off Nausea, If You’re Not A Morning Eater
Nobody likes feeling sick and nauseous when they’re trying to exercise — and if you’re not a morning eater, fasted exercise could be a great way to get in your workout without feeling like you’re going to be sick.
Working Out On An Empty Stomach – Cons
Unfortunately, the cons of working out on an empty stomach outweigh the pros for most people. Here are a few reasons why fasted exercise may not be ideal:
The Fat-Burn Potential Isn’t Significant
While there’s some evidence that fasted cardio can help you burn more fat, the gains are small — and they only apply to cardio, not resistance training (1).
Furthermore, fat burning isn’t the most efficient use of your energy. And we all know that the human body is far more complex than simply “burning fat.”
So if you’re looking to achieve more with your workouts, don’t be fooled by the promise of fat-burning benefits — they may not be as significant as you think.
You’ll Miss Out On Excess Post-Exercise Oxygen Consumption
The downside is, it only happens when you’ve exercised at a relatively high intensity for at least 30-45 minutes — and when you’re exercising on an empty stomach, it can be difficult to reach that level.
Think about it—is the promise of burning a few extra fat calories really worth the risk of missing out on greater gains? We don’t think so.
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You Might Feel Too Weak To Exercise
When you’re in a fasted state, there’s not an adequate supply of carbs for energy — and that could leave you feeling weak and lethargic throughout your workout.
If you’re planning on doing a tough HIIT session or lifting heavy weights, fasted exercise may not be the best option.
You Might Lose Hard-Earned Muscle
The human body is a lot like an engine — it needs fuel to run efficiently. When you’re in a fasted state, your body isn’t receiving the macros it needs to function optimally — and this could lead to muscle loss. That’s when your body breaks down protein stores to use as energy.
Most young people with a high fitness level and good body composition could get away with it, but for the average joe, it’s not worth the risk. Seniors should especially look out for this, as their muscles are already more prone to breakdown.
In short — if your goal is to build muscle and maintain a lean physique, fasted exercise may not be the best option.
You Might Not Progress As Quickly
When you work out in a fasted state, your body lacks the resources it needs to grow and become stronger. That’s why many bodybuilders and serious athletes prefer to work out after eating a meal — it helps them get the most out of their workouts and progress quickly.
You’ll Trigger Stress Hormones
Exercising on an empty stomach triggers stress hormones, like cortisol. These hormones can be beneficial — they trigger fat burning and help you stay alert.
Not to mention the link between high cortisol levels, cravings, and increased fat storage (6). You might find yourself ravenously craving foods you’d normally be able to resist.
You’ll Take Enjoyment Out Of Your Workouts
If you’re anything like us, then the idea of working out on an empty stomach just doesn’t seem that appealing. Without the proper fuel, it’s hard to stay focused and enjoy the process.
We believe that in order for exercise to be effective, you need to actually like doing it. That’s why we recommend eating a meal before your workout — not only will it make you feel good, but you’ll also be able to perform better. And when you see results, that’s when it all becomes worth it.
What Should You Eat Before A Workout?
It’s usually best to eat a light meal or snack about an hour or two before exercising so your body has time to digest. This will ensure you have enough energy to get the most out of your workout.
The best pre-workout snacks include a combination of carbs and protein. It’s also important to stay hydrated before and during your workout. Below are some of our favorite pre-workout meals and snacks:
- Oatmeal with peanut butter, banana slices, and a scoop of protein powder
- Greek yogurt with berries and nuts
- A smoothie made with banana, protein powder, almond milk, and peanut butter
- Toast with avocado and an egg
- A handful of trail mix or granola with nuts and dried fruit
- Hummus with carrot sticks and celery
- An apple with nut butter
Ultimately, the best pre-workout snack is one that you enjoy and that provides your body with enough energy to finish your workout.
Is It Ok To Drink Pre Workout On An Empty Stomach?
If you’re looking for a quick energy boost before your workout, then pre-workout drinks are an option.
But it’s important to note that many pre-workout drinks contain large amounts of caffeine and other stimulants. That’s why it’s often best to avoid them on an empty stomach — they could cause an upset stomach or nausea (2).
If you do decide to take a pre-workout drink, make sure to read the label for dosing instructions. And it’s always a good idea to pair your pre-workout drink with a light snack before you work out.
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When Should You Eat Before A Workout?
Timing is an important factor when it comes to pre-workout meals. Eating too close to your workout could cause gastrointestinal distress, while eating too far away could leave you feeling tired and sluggish.
For the average person, eating a meal or snack about an hour before your workout should give you plenty of energy and prevent any stomach issues. If the meal is particularly large or contains high-fiber foods, then it’s best to eat a few hours before your workout.
The Bottom Line
Working out on an empty stomach can be beneficial, but it’s not suitable for everyone. Fasted exercise is not the best way to promote muscle growth and maintain a lean physique.
We recommend consulting a nutritionist or doctor before deciding if fasted exercise is right for you. And regardless of whether or not you choose to give it a try, always stay hydrated and make sure you’re getting the nutrients you need to reach your fitness goals.
This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!
- Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis (2016, cambridge.org)
- Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update (2022, nih.gov)
- Effects of exercise intensity and duration on the excess post-exercise oxygen consumption (2006, pubmed.gov)
- Exercising in the Fasted State Reduced 24-Hour Energy Intake in Active Male Adults (2016, nih.gov)
- Physiology, Cortisol (2022, nih.gov)
- Stress, cortisol, and other appetite-related hormones: Prospective prediction of 6-month changes in food cravings and weight (2018, nih.gov)