There are countless myths and theories about whether or not you should eat breakfast before a workout, and that one may be more beneficial than the other. Some say working out on an empty stomach helps to burn more fat. But, what really happens inside of your body?
As someone who has been studying exercise science and human physiology in university for a few years now, I’m able to come to a conclusion about this issue. Without getting too in depth, the following information (backed up by science!) will enlighten you about the processes your body goes through when you eat and when you don’t eat before you exercise. Should you eat before a workout to burn fat quicker? We’ll answer this below. If you’re in a rush to find out, scroll down to The Final Verdict. 🙂
Let’s review a bit of science first.
How do you gain fat?
As you eat throughout the day, you’re consuming:
When you eat carbohydrates, they get digested and converted to glucose in your blood. This glucose in your blood is now readily available for your body to use for energy. Glucose must be maintained within a very narrow range.
Under extreme conditions, if there’s highly excessive glucose in your blood, your body will be unable to absorb this glucose and this is how diabetes arises. At this point, excess glucose will be excreted in the urine. If there’s too little glucose in your blood, this can be dangerous or even deadly, as glucose is the only fuel your brain can use for energy (except in times of starvation where your brain can begin to use the acidic ketone bodies which we won’t get into for our purposes). So, glucose levels in your blood must be balanced.
Excess glucose is stored as glycogen or used by muscles (during training). If you’re not exercising, your muscles aren’t using up the blood glucose from the meals you’re eating. This glucose will either be stored as glycogen or triglycerides (which is stored fat). Since the body’s ability to store glycogen is limited, most of the excess glucose is converted to triglycerides and stored in adipose tissue.
Let’s Recap: Carbs from your meal are digested and absorbed as glucose in your blood. This glucose is used as energy for your body, especially your muscles. If you don’t exercise, this excess blood glucose will either be stored as glycogen or triglycerides (AKA fat). Since glycogen stores are limited, most excess glucose will be stored as triglycerides– which is basically fat.
Now, let’s break down metabolism (which is the total chemical reactions that occurs in your body) into 2 states:
- Fed-State: This is the time period following a meal when the food being digested (so you’ve been fed– hence the name) are being absorbed and stored for energy for the tissues to use later.
- Fasted State: This is the time period when nutrients from a previous meal are no longer available in the blood for use by tissues. The pool of available nutrients in the blood has gone down since you haven’t eaten in a while so the body ends up tapping into its reserves and breaking down the stored goodies in order to provide energy now.
Many people decide to wake up in the morning and jump straight into cardio without eating breakfast, claiming that this will allow them to burn more fat. When you first wake up, your body is in a fasted state. This means that your glycogen (which is stored carbohydrate) is being depleted because your body has been breaking it down to glucose to fuel your bodily functions throughout the night (such as fueling your brain). Glucose from carbohydrates is the body’s preferred source of energy but now, since glycogen stores have been reduced, glucose isn’t readily available for use by your body. So, your body prioritizes the burning of fats for energy instead.
This is why many people believe that working out before eating breakfast in the morning is great for burning fats– because glycogen stores have been reduced so now that body ends up burning fat instead of glucose.
However, it’s not that simple.
If you’ve been sleeping for 8 hours or more and haven’t eaten in quite a while, there is a great chance your glycogen stores are now completely depleted. At this point, when your body has no more glucose available to fuel your body, it will break down your muscle tissue into amino acids which are then sent to the liver to produce glucose (in a process called gluconeogenesis). This is when you’ll begin to lose muscle mass and will result in less muscle tone and definition. Don’t worry though! This scenario only results from extreme starvation or serious malnutrition.
If you’re one of those busy bodies who sleeps less than the recommended 8 hours, or if you have eaten just a few hours before you slept, the above scenario would most likely not happen. So, if you wake up and begin your cardio workout without eating breakfast first, some glycogen would still be available in your body, allowing for the burning of fat for fuel (without using any of our muscle tissues– yay!)
So, how do we burn fat?
To keep things simple, basically, fats are stored as triglycerides in adipose tissue all over your body, which we mentioned earlier. In order to burn fat, the triglycerides must be broken down into fatty acids and glycerol. Glycerol goes to the liver and can then be converted to glucose for energy production. Meanwhile, the fatty acids are released into the blood where they can be taken up by muscle tissues, where they will be burned (or oxidized) for energy! However, fatty acids can ONLY be burned for energy if there is oxygen present. So, the amount of oxygen available determines your body’s ability to burn fat.
The Final Verdict: Should you eat breakfast before you exercise?
If you eat a large meal before your workout, chances are you won’t feel very well during your workout– I know I don’t. This is because blood is being diverted away from your working muscles to help with digestion. Since blood carries oxygen, blood being diverted away from the working muscles means less oxygen is available to the muscles. Less oxygen available to the muscles means that fat won’t be burned as quickly or efficiently.
On the other hand, assuming that you are not in starvation mode or malnourished, working out on an empty stomach is more likely to burn fat quicker since your body is not preoccupied with digestion. So, more oxygen is available for the working muscles to burn fat. However, training on an empty stomach will probably have you feeling ill and lacking in energy during your workout.
If skipping a meal before your workout makes you feel ill and lethargic, eating a light meal beforehand is a great alternative (and one I’d personally vouch for). Eating an apple, energy bar or drinking a fruit smoothie 30 minutes before you exercise will provide you with energy and they are quick and easy to digest!
Either exercising on an empty stomach or exercising after a light meal will allow blood to deliver as much oxygen as possible to your muscles since your body isn’t preoccupied with digestion. More oxygen to your muscles means your body will potentially burn more fat. But, I’d personally recommend eating a light meal before exercising to keep you feeling energetic and active throughout the entire duration of your workout.
If you prefer to train after a larger meal (like dinner), make sure to wait at least 2 hours before exercising. A larger meal means more fat and protein contents which results in slower digestion. Waiting at least 2 hours before training will ensure that digestion has gone to completion, allowing for working muscles to receive as much oxygen as possible to be able to burn more fat.
Get to know your body before making a clearcut decision about whether or not you should eat before exercising. Depending on how you feel before a workout, you can make a decision about whether or not you should eat. Eating a large meal beforehand may have detrimental effects on how you feel during your workout. Not eating at all may also have detrimental effects on your training and have you feeling lethargic. Having a small snack before you exercise may work for you instead.
Make sure to take care of your body and listen to your body’s demands! I hope this information educated you guys a bit more regarding this issue and helped you make a decision about whether or not you should eat before a workout. Let me know if this helped you in the comments section below! Be sure to share this with your friends and family if it did!
Hope you guys have a very sweaty workout. 🙂