It is a truth universally acknowledged that what you eat and how you exercise affects not just your weight, but your overall body composition. Being true though doesn’t always mean quick fixes or easy answers.
After all, when we talk about diet and exercise, we’re talking about an industry of diverse research and opinions leading to different nutritional plans, questions on suitable supplements and a varied landscape of exercise that range from low-intensity stretches to high-intensity and high-impact training.
While we can (and do!) talk about the benefits and risks of many different types of diet and exercise, today, let’s take a look at what happens when you don’t eat before a workout. Let's take a look at fasted cardio exercise.
What is fasted cardio?
In many ways, fasted cardio is exactly what it sounds like. It’s the act of fasting, or abstaining from all food and drink that isn’t water, before performing cardio exercise on an empty stomach.
The best time to do this is usually after you wake up. That period around, and including, when you sleep without eating or drinking is often referred to as a daily fast or an overnight fast and lasts generally between 8 to 12 hours [1].
This means a morning workout after you get up and before you eat breakfast or have that cup of coffee is considered a type of fasted exercise, and like all types of exercise, it has both potential health benefits and risks.
But what exactly is a fasted workout hoping to achieve? And how does it improve body composition?
The impact fasted cardio has on you
The idea underpinning the benefits of a fasted cardio session is, put simply, that your body might burn more stored body fat if you haven't eaten recently.
Early studies have found that fasted cardio burn can induce higher fat oxidation. Fat oxidation refers to the various processes that cause your body to generate energy for bodily functions such as muscle contraction and the repair of body tissue — two functions crucial to the building of muscle mass.
When you eat, you are replenishing your body with glucose which it will then use as its primary energy source for your workout, whereas by fasting, your body instead will use stored fat to get you moving [1].
On top of that, there is also evidence that consistent fasted exercise can lead to chronic molecular adaptations within your body that are overall favourable to fat oxidation [2].
In other words, it may help to rewire how your body uses fat beyond just the fasted aerobic exercise.
Is fasted cardio effective?
While the impact of fasted cardio workouts on fat stores has been proven, whether or not that actually equates to weight loss and body recomposition is a bit of a trickier question.
Overall, most studies have found that there's not much difference between a fasted workout and a fed workout. At the end of the day, dietary change and the act of working out itself is generally what impacts fat loss and the growth of muscle tissue, whether you eat before exercise or not [1].
That said, there may be other benefits of fasted cardio that see you experiencing great results.
The benefits of fasted cardio
While fasted cardio workouts may not result in greater weight loss than a non-fasted cardio workout, the research does show that you will likely still be burning fat at a slightly higher rate.
On top of that, research has also found that fasted workouts can impact blood sugar levels, with one study finding that people with a fasted cardio habit had significantly reduced fasting insulin levels and increased insulin sensitivity, which reduces the risk of diabetes [3].
The risks of fasted cardio
There are very few risks to fasted cardio, and many of them are dependent on the type of exercise you are doing and on just how empty your stomach is.
In particular, the biggest risk is side effects associated with low blood sugar. These side effects often manifest when exerting yourself in high-intensity exercise or a longer endurance aerobic session, and may appear as dizziness, shaking, nausea, spots before the eyes, vomiting or even fainting.
They can also manifest as fatigue, which one study has found is slightly more common in fasted cardio workouts than in non-fasted cardio exercise [3].
Ultimately, the risks are dependent on the type of exercise that you're doing, and for how long you're doing it.
Listening to your body as you work out is always vital, and knowing the difference between pushing yourself to the next level, and pushing yourself past the limit, is something everyone should learn. If you feel lightheaded or nauseous during exercise, slow down, rest and give yourself the chance to recover.
What to eat after a fasted cardio workout
Whether you are coming out of an overnight fast or are engaged in an intermittent fasting diet, what you eat after a fasted cardio workout is crucial to reaping the rewards of your exercise and maintaining a healthy lifestyle.
In particular, it's important to avoid sugars and refined grains where you can, as these can undo the work of any workout.
Research indicates that the best way to get your digestive system working well and to support your body in recomposition post-exercise is to eat fruits, vegetables, beans, lentils, whole grains, lean proteins and healthy fats [4].
Depending on what time of day you've done your fasted cardio exercise, this might change what that looks like.
If you've done your overnight fast, have hit the gym for your early morning workout, and are ready for breakfast, focus on a lighter meal rich in protein and whole grains such as:
- Oatmeal with chopped nuts or nut butter, fruit, milk and ground flaxseed
- Plain Greek yoghurt with raspberries, blueberries or strawberries, with added granola, chia seeds and nuts
- Zucchini fritters with smoked salmon and a poached egg
- Boiled eggs with leafy greens
- Fruit and vegetable-based smoothies with added protein powder.
If you are an intermittent faster and working out later in the day, why not try:
- Brown rice or quinoa with roast vegetables and a serve of lean meat, egg, tofu or plant-based meat
- Falafel and cucumber salad in a pita pocket
- A creamy, healthy tuna pasta salad with fresh dill and avocado
Or if you're after a snack, why not try a piece of fruit, hummus and vegetables, or tuna and crackers?
If you're looking for support or advice on fasted cardio and other exercise programs, the Compound Program may be just what you need.
Once the exclusive domain of billionaires and Hollywood stars, we're on a mission to make premium concierge care accessible to every man who wants more.
Equipped with leading diagnostic reporting, Compound's team of dedicated healthcare professionals and expert specialists is guaranteed to help you access the future of proactive healthcare and reach your health goals.
We take a multi-disciplinary approach to health optimisation and preventative care to help men unlock barriers to everyday performance. Our team of dedicated healthcare professionals and expert specialists are here to help you access the future of proactive healthcare, today.
This post contains general information about health and wellness practices. It is not intended as medical advice and should not be treated as such. Please consult with a healthcare professional before starting any new health regimen. This information is provided without any representations or warranties, express or implied.
It is a truth universally acknowledged that what you eat and how you exercise affects not just your weight, but your overall body composition. Being true though doesn’t always mean quick fixes or easy answers.
After all, when we talk about diet and exercise, we’re talking about an industry of diverse research and opinions leading to different nutritional plans, questions on suitable supplements and a varied landscape of exercise that range from low-intensity stretches to high-intensity and high-impact training.
While we can (and do!) talk about the benefits and risks of many different types of diet and exercise, today, let’s take a look at what happens when you don’t eat before a workout. Let's take a look at fasted cardio exercise.
What is fasted cardio?
In many ways, fasted cardio is exactly what it sounds like. It’s the act of fasting, or abstaining from all food and drink that isn’t water, before performing cardio exercise on an empty stomach.
The best time to do this is usually after you wake up. That period around, and including, when you sleep without eating or drinking is often referred to as a daily fast or an overnight fast and lasts generally between 8 to 12 hours [1].
This means a morning workout after you get up and before you eat breakfast or have that cup of coffee is considered a type of fasted exercise, and like all types of exercise, it has both potential health benefits and risks.
But what exactly is a fasted workout hoping to achieve? And how does it improve body composition?
The impact fasted cardio has on you
The idea underpinning the benefits of a fasted cardio session is, put simply, that your body might burn more stored body fat if you haven't eaten recently.
Early studies have found that fasted cardio burn can induce higher fat oxidation. Fat oxidation refers to the various processes that cause your body to generate energy for bodily functions such as muscle contraction and the repair of body tissue — two functions crucial to the building of muscle mass.
When you eat, you are replenishing your body with glucose which it will then use as its primary energy source for your workout, whereas by fasting, your body instead will use stored fat to get you moving [1].
On top of that, there is also evidence that consistent fasted exercise can lead to chronic molecular adaptations within your body that are overall favourable to fat oxidation [2].
In other words, it may help to rewire how your body uses fat beyond just the fasted aerobic exercise.
Is fasted cardio effective?
While the impact of fasted cardio workouts on fat stores has been proven, whether or not that actually equates to weight loss and body recomposition is a bit of a trickier question.
Overall, most studies have found that there's not much difference between a fasted workout and a fed workout. At the end of the day, dietary change and the act of working out itself is generally what impacts fat loss and the growth of muscle tissue, whether you eat before exercise or not [1].
That said, there may be other benefits of fasted cardio that see you experiencing great results.
The benefits of fasted cardio
While fasted cardio workouts may not result in greater weight loss than a non-fasted cardio workout, the research does show that you will likely still be burning fat at a slightly higher rate.
On top of that, research has also found that fasted workouts can impact blood sugar levels, with one study finding that people with a fasted cardio habit had significantly reduced fasting insulin levels and increased insulin sensitivity, which reduces the risk of diabetes [3].
The risks of fasted cardio
There are very few risks to fasted cardio, and many of them are dependent on the type of exercise you are doing and on just how empty your stomach is.
In particular, the biggest risk is side effects associated with low blood sugar. These side effects often manifest when exerting yourself in high-intensity exercise or a longer endurance aerobic session, and may appear as dizziness, shaking, nausea, spots before the eyes, vomiting or even fainting.
They can also manifest as fatigue, which one study has found is slightly more common in fasted cardio workouts than in non-fasted cardio exercise [3].
Ultimately, the risks are dependent on the type of exercise that you're doing, and for how long you're doing it.
Listening to your body as you work out is always vital, and knowing the difference between pushing yourself to the next level, and pushing yourself past the limit, is something everyone should learn. If you feel lightheaded or nauseous during exercise, slow down, rest and give yourself the chance to recover.
What to eat after a fasted cardio workout
Whether you are coming out of an overnight fast or are engaged in an intermittent fasting diet, what you eat after a fasted cardio workout is crucial to reaping the rewards of your exercise and maintaining a healthy lifestyle.
In particular, it's important to avoid sugars and refined grains where you can, as these can undo the work of any workout.
Research indicates that the best way to get your digestive system working well and to support your body in recomposition post-exercise is to eat fruits, vegetables, beans, lentils, whole grains, lean proteins and healthy fats [4].
Depending on what time of day you've done your fasted cardio exercise, this might change what that looks like.
If you've done your overnight fast, have hit the gym for your early morning workout, and are ready for breakfast, focus on a lighter meal rich in protein and whole grains such as:
- Oatmeal with chopped nuts or nut butter, fruit, milk and ground flaxseed
- Plain Greek yoghurt with raspberries, blueberries or strawberries, with added granola, chia seeds and nuts
- Zucchini fritters with smoked salmon and a poached egg
- Boiled eggs with leafy greens
- Fruit and vegetable-based smoothies with added protein powder.
If you are an intermittent faster and working out later in the day, why not try:
- Brown rice or quinoa with roast vegetables and a serve of lean meat, egg, tofu or plant-based meat
- Falafel and cucumber salad in a pita pocket
- A creamy, healthy tuna pasta salad with fresh dill and avocado
Or if you're after a snack, why not try a piece of fruit, hummus and vegetables, or tuna and crackers?
If you're looking for support or advice on fasted cardio and other exercise programs, the Compound Program may be just what you need.
Once the exclusive domain of billionaires and Hollywood stars, we're on a mission to make premium concierge care accessible to every man who wants more.
Equipped with leading diagnostic reporting, Compound's team of dedicated healthcare professionals and expert specialists is guaranteed to help you access the future of proactive healthcare and reach your health goals.
We take a multi-disciplinary approach to health optimisation and preventative care to help men unlock barriers to everyday performance. Our team of dedicated healthcare professionals and expert specialists are here to help you access the future of proactive healthcare, today.
This post contains general information about health and wellness practices. It is not intended as medical advice and should not be treated as such. Please consult with a healthcare professional before starting any new health regimen. This information is provided without any representations or warranties, express or implied.
Ready to optimise for success?
You'll also receive a reading list of what we're keeping our eye on at Compound HQ as well as news and product updates as our offering progresses.
