People who work out in the morning may have a tough time reaching peak (or even moderate) performance, especially if the run they're doing is either high intensity or long in duration. This is because your body is in a fasted state, and you lack the energy you'd need to fuel the workout—energy that comes from food.
Provided you ate plenty of carbs the day before, there's no problem running first thing without having breakfast - your liver glycogen stores will be somewhat depleted but your muscle glycogen stores will be fine as you've been resting.
it is generally safe to exercise while fasting. In fact, some people find that they have more energy and focus while fasting, which can make it a great time to exercise.
When you run on an empty stomach, your body may not have enough fuel to sustain your workout, which can lead to decreased performance and an increased risk of injury. Eating a nutritious breakfast can help provide the energy and nutrients your body needs to exercise at its best.
Yes, it is completely safe and is, in fact, recommended. You burn more fat and build more muscle if you workout during your fast. This is why you work out to begin with, and both effects are improved. There are other benefits as well.
Yes, it is OK to work out while fasting because the key to weight loss and muscle gain is not just calories and exercise, but hormone optimization. Studies demonstrate amazing benefits to intermittent fasting alone, but combining fasting with sprint training takes the benefits of each to a whole new level.
You Should Train While Fasting
Even if your main goal is losing fat, you still need to lift, which prevents your body from burning through muscle to fuel your daily activities. You won't gain much muscle if you're fasting, but if you lift, you won't lose it, either.
According to a 2016 study published in the Journal of Nutrition and Metabolism participating in a morning run after an overnight fast can increase fat oxidation during exercise and help you to decrease food intake over the 24 hours following exercise.
For example, a systematic review and meta-analysis published in 2016 in the British Journal of Nutrition states that an aerobic workout performed in a fasted state leads to greater fat oxidation, compared to a cardio workout done after eating.
But if you're planning on running for more than 60 minutes or doing intense intervals on a totally empty stomach, you might find yourself feeling slow, lethargic, or even lightheaded without eating, Scott explains.
What the research says. A beta-analysis from 2017 looking at five studies on fasted versus fed exercise concluded that working out fasted does not result in greater weight loss or changes in lean muscle mass or fat mass.
However, the good news is that running is one of the best forms of exercise to lose belly fat, and there are even a few small tweaks you can make to your regular running schedule to deliver a sustained fat burning boost.
When you exercise in a fasted state — after a night's sleep and before you eat breakfast — then you do actually use more fat as a fuel source during exercise. But research from my team has shown that performing exercise in a fasted or fed state does not have any meaningful impact on body fat in the medium to long term.
While running fasted for a short, low-intensity run may not be an issue, as the duration and intensity of a run increases, a review of 46 studies found that consuming enough carbohydrates prior to and during a run is needed to keep energy levels up and improve performance.
The verdict? It's clear that fasted cardio is really only beneficial for those who struggle with stomach discomfort if they've eaten too close to a workout, or simply don't have time before their morning sweat session to devour breakfast or a pre-workout snack.
Improves Your Productivity for the Day
It not only increases your alertness, but also helps you get out of bed at the right time. After a good run, more adrenaline and endorphins flow through the body. This results in an exquisite feeling called “runner's high”, which can last for hours after you finish your workout.
Many folks can do moderate runs lasting less than an hour on an empty stomach with no problem. (Though you certainly can eat beforehand if you want to.) But if you're going longer or are doing something intense like intervals, hills, or speedwork, it's a good idea to get something in your stomach, says Scott.
When you first wake up, you're a little dehydrated from your night of sleep, so it's a good idea to drink some water before a morning run. But you don't have to drink a ton—you don't want it jostling around in your stomach, after all. Even a few sips can help fight off fatigue during and after your run, Stefanski says.
A morning workout may promote better quality of sleep as compared to afternoon or evening workouts. In fact, the authors of a 2014 study published in Vascular Health and Risk Management concluded that early morning may be the most beneficial time to engage in aerobic exercise.
At just 30 minutes of regular running, you'll reap many rewards: Improved Cardiovascular Health: Running is an excellent aerobic exercise that helps strengthen the heart and improve cardiovascular health. Regular running can lower blood pressure, reduce the risk of heart disease, and improve circulation.
Is Working Out On an Empty Stomach Bad for You? According to Roper, fasted exercise is generally safe for most people, but it may lead to side effects. “Because blood glucose gets depleted during fasting cardio, you can experience some side effects including lightheadedness and dizziness,” she said.
Extended fasting periods without adequate nutrition can lead to muscle loss, fatigue, impaired performance, and potential health risks. If you want to work out while fasting, the safest bet is to stick to daily 12–18-hour fasts and get that workout done first thing in the morning!
Some experts may recommend females fast for 14 hours and slowly build their way up to 16 hours, while males can start fasting for 16 hours straight away. This type of intermittent fast may be helpful for someone who has already tried the 12-hour fast but did not experience any benefits.
Exercising in a fasted state may burn some quick body fat, but it's not the best option for your body in the long-run. Eat a small snack or meal before and after your workout to ensure that you're properly fueled to perform your best in the gym and recover quickly when you get home.