Running on an empty stomach forces the body to tap into its fat stores for energy. When glycogen levels are low, the body resorts to burning fat as fuel. This can be advantageous for runners aiming to improve their body composition or enhance their fat-burning capabilities.
The theory of fasted runs is that they improve fat oxidation and increase the amount of glycogen that you store in your muscles, allowing you to be more aerobically efficient at multiple intensities.
Running on an empty stomach can help your body burn fat as fuel, which can be beneficial for weight loss goals. But if you're doing a longer, more intense workout, running on an empty stomach can be risky. Without enough fuel in your system, you might experience dizziness, fatigue, and even fainting.
Running on an empty stomach can help your body burn fat as fuel, which can be beneficial for weight loss goals. But if you're doing a longer, more intense workout, running on an empty stomach can be risky. Without enough fuel in your system, you might experience dizziness, fatigue, and even fainting.
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.
However, exercising on an empty stomach will also cause you to lose lean muscle mass at the same time, which can hinder long-term weight loss. Exercising without eating first can cause dramatic shifts in your blood sugar, and when it drops quickly you can feel nauseous, light-headed or dizzy.
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.
You might be wondering, how long does it take for your stomach to empty? After a meal, it normally takes around 1 hour and 30 minutes to 2 hours for your stomach to empty. But, the type of meal you eat plays a role in how fast it moves through your stomach.
Running without prior food intake can induce fatigue due to these factors. To mitigate risks during initial fasted runs, it's wise to carry some form of quick energy, such as sugar, a cereal bar, or a portable compote.
“Walking and jogging tend to increase gastric motility and gastric emptying in everyone; this is a physiologic response,” Dr. Smith says. “Movement gets the digestive system moving a little more quickly than if you're sitting still.
Eat a mix of simple and complex carbs one to two hours before you run or a snack 15-30 minutes before. Eat 60 grams of simple carbs, like sports gels or pureed fruit, for every hour you run. One to two hours after, eat a meal with 20 grams of protein and about 60 grams of complex carbs.
While scientific studies have found limited support for the theory behind fasted cardio, other research has found that athletes who fast have experienced measurable fat loss.
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.
Hunger alone cannot exactly burn fat. Just being hungry does not mean your body is burning fat. The body uses sugar for energy in case of hunger and not the fat reserve. It might play a small role, though.
Running does get a little easier the more often you do it, and you'll likely be able to build up in distance by running daily. But just like any type of workout, running the same distance and speed every day can lead to a plateau where you're unable to improve your pace or increase your mileage.
Longer periods without food, such as 24-, 36-, 48- and 72-hour fasting periods, are not necessarily better for you, and may be dangerous. Going too long without eating might actually encourage your body to start storing more fat in response to starvation.
Eating bananas on an empty stomach can provide an immediate energy boost and essential nutrients, but it may impact blood sugar levels. Pairing bananas with other foods like yogurt or oats can enhance nutrient absorption and minimize potential side effects.
Running can help to create a caloric deficit, which may reduce the padding around your abdomen (but remember, some fat is necessary to cushion vital organs). Sprinting in particular requires your abdominals to contract more forcefully, which may increase muscle size, Buckingham said.
But long runs alone aren't going to help you shed that belly fat. You also need to make dietary and lifestyle changes to shift those problem areas. Even if you're a regular runner who is watchful of what you eat, it's still possible to have belly fat that you just can't shift. In many cases, this can be down to diet.
So, running on an empty stomach helps our muscles use fat for fuel. This habit is great for burning more fat. By exercising without blood sugar, our body learns to use stored fat. This allows us to run longer and perform better, thanks to the energy from fat.
Flush Out Toxins
Toxins from pollution, UV exposure, smoking, sugars, and other factors can lead to skin inflammation, acne, early signs of aging, and more. Increased blood flow and lymphatic drainage during exercise helps to remove these toxins from the body to prevent further skin damage.
Simple and Complex Carbs
Simple carbohydrates, like a handful of HIGH5 Energy Gummies or a ripe banana, are ideal for a quick energy boost at the start of the race, and they're also good to use throughout the run. They provide readily available fuel for that initial burst of speed and sustained energy during the race.