Does exercising on an empty stomach maximize fat burning?

Dear Reader,

To eat, or not to eat (before exercise), that is the question—and it’s a complicated one! Although working out on an empty stomach may cause your body to burn more fat in the short term, that doesn’t mean you’ll lose body fat in the long term. Exercising without eating may interfere with your exercise goals and make losing fat challenging. Unfortunately, there are no fast and easy rules for how to integrate nutrition and exercise. You may consider discussing your specific situation with a diet or fitness professional. Read on if you want to flex your knowledge about food and exercise!

What happens if you exercise on an empty stomach?

When you eat carbohydrates, your digestive system breaks them down into glucose. Glucose is used as your body’s primary energy source. However, if you exercise on an empty stomach, you’ll have less glucose immediately available to use for energy. As a result, your body may shift to using more fat—or what’s considered the body’s ‘stored fuel’—than usual to provide you with energy which will power you through your workout.

Does exercising on an empty stomach make you lose fat?

While burning more fat during a workout may seem beneficial, several studies have found that exercising while fasting doesn’t lead to more overall fat loss. The amount of extra fat that you might burn while exercising on an empty stomach is quite small compared to the amount of fat that’s stored on the body. Additionally, fat loss takes place over a longer period of time, even if you exercise regularly. So, while you might temporarily switch to burning more fat when exercising on an empty stomach, actually losing that body fat for good mostly depends on longer-term factors in your life. This includes the overall balance between how much energy (in calories) you consume and how much you burn, rather than when you do either.

What are the downsides of exercising on an empty stomach?

While you might use more fat as a source of energy during your workout, exercising on an empty stomach may also lead to unintended consequences including:

• Muscle loss: If you’re doing high-intensity exercise, like heavy weight training or fast running, your body may struggle to get the energy it needs from fat alone. Without the glucose you would have gotten from eating, your body may rely on using protein and carbohydrates stored in your muscles. This may cause you to lose muscle mass. 
• Less effective exercise: People who exercise on an empty stomach often report feeling light-headed, nauseous, and easily tired. With high-intensity exercise, working out without eating may worsen your endurance and the effectiveness of your exercise. 
• Burning fewer calories: As a result of decreased exercise performance because of the lack of carbs available to use for energy, you may burn fewer calories if you’re working out on an empty stomach. This may make it harder to lose body fat.  
• Post-exercise hunger: Exercising on an empty stomach may increase how hungry you feel after working out. This may lead you to consume more calories overall than if you were to eat before exercising. 

How can you support your exercise by eating and drinking?

Eating nutritious foods and drinking lots of water can benefit your exercise and help you achieve your goals. It may be useful to consider: 

• Eating before and after exercise: It’s recommended that you eat a snack or small meal high in carbohydrates around one to three hours before exercising. If it’s been a while since your last meal, a snack like a banana or a piece of toast can help boost your exercise performance. After working out, having a meal including carbohydrates and protein may help your body recover and get stronger. 
• Drinking fluids before, during, and after exercise: While you’re exercising, it’s recommended to drink between half a cup and one cup of water every 15 to 20 minutes. You may want to consider also drinking two or more cups of water before and after exercising.  If you are exercising for longer than an hour, you might find it useful to have a sports drink containing carbohydrates and electrolytes. 

List adapted from Mayo Clinic 

Ultimately, there isn’t just one correct way to pair eating and working out. Exercising is generally good for your overall health, and it’s great to keep it up in a way that feels sustainable to you and your lifestyle! If you’re interested in learning more or hoping to figure out a plan that’s best for your goals, consider meeting with a registered dietitian or a personal trainer. 

Good luck!