A common question runners come upon: running on an empty stomach- yes or no? Everyone you talk to has an opinion on this topic. For some, this is a regular part of their training, while others refuse to exercise on an empty stomach. In this blog post, we’re diving into the three big myths and the truth behind them.
Working out on an empty stomach can lead to muscle loss
In general, people think working out without eating breakfast leads to muscle loss. But good news! Your muscles won’t disappear right away. Often, people (wrongfully) assume that without food, your body lacks the necessary carbohydrates and glucose for a morning training session. According to this view, the body must break down muscle protein to get the energy it needs to power through a workout. So, in simple terms, the body loses muscle. Buuuut this is not exactly true: The body stores glucose in the form of glycogen in the liver and muscles. Throughout the night, the body’s levels of insulin and liver glycogen decrease. However the body still has the muscle glycogen stores. So when you wake up and go without food, your body initially gets its energy from the glycogen stored in your muscles.
As your workout continues, the stores of glycogen in your muscles are virtually exhausted. Thus your body needs to find a different supply of energy and it resorts to free fatty acids for fuel. Now if you crank up your workout (to more than the 100% you were already giving of course), your body will also obtain the energy it needs by breaking down proteins. At this point you run the risk of losing muscle. But most runners will have stopped their workout by this point.
Working out on an empty stomach is the best method to lose weight
An empty stomach workout is often recommended as the best way to burn fat and lose weight. While properly running on an empty stomach can eventually force your body to increasingly obtain the energy it needs from free fatty acids, this is not the decisive factor in losing weight.
The percentage of energy created from burning fat is high, but the total energy expenditure, and thus calorie consumption, are relatively low due to the low training intensity. In workouts like high-intensity running or interval training, the percentage of energy produced by burning fat is significantly lower. But the total energy expenditure and calorie consumption are many times higher. All in all what matters most in weight loss is the energy balance: if you burn more calories than you consume, you’ll lose weight. Thus, high-intensity running sessions are preferable to running on an empty stomach when it comes to losing weight.
Running on an empty stomach increases your endurance
Working out on an empty stomach is not a good idea for leisure athletes who want to improve performance. Training duration as well as intensity are severely restricted by the lack of glycogen. Because of this, the intended training stimulus is rather low. A high-quality workout that lasts longer at a higher intensity is much better for increasing one’s performance.
Studies on professional athletes have shown that extremely positive effects can be achieved by specific workouts with emptied glycogen stores. This will cause your body to optimize and economize its fat metabolism. Our bodies can learn to do longer with the glycogen stored in our muscles. But there is no substantial evidence proving that this leads to improved race performance. Keep in mind, however, that regular training with previously emptied glycogen stores can seriously harm your health.
So if you want to run on an empty stomach, we recommend:
- Your run should last between 40 and 60 minutes, depending on your fitness level.
- You should choose a low intensity level (perhaps a recovery run or a conversation pace).
- You should drink a big glass of water before your run.
Another tip: for your breakfast afterwards, make sure to take advantage of the anabolic window (aka the Open Window) in the first 30 minutes after your workout. At this time your body can absorb nutrients much faster than usual, so it can optimally replenish its empty stores.