Buzz
You’ve probably experienced that sluggish feeling when you try to hit the gym after a big meal, wishing you’d skipped that pre-workout snack. However, exercising on an empty stomach isn’t the best option either. Here’s why fueling up before your workout can be more beneficial than you think.
The science behind it
Imagine it’s time for your workout. Do you eat first or wait until you’ve finished your routine? Some advocates of fasting before exercise claim it can help speed up fat loss. For example, a study published in the British Journal of Nutrition found that participants who exercised while fasted burned almost 20 percent more fat than those who ate beforehand. Similarly, another study published in the International Journal of Sports Nutrition and Exercise Metabolism showed that aerobic exercise in a fasted state reduces body fat percentage and weight more effectively than when participants ate before training.
Why does the fat burn faster? According to sports dietetics expert Kelly Pritchett, Ph.D., R.D., your body switches its fuel source. When engaging in strenuous activities like long-distance running or weightlifting, your body relies on glycogen, or stored carbohydrates, for energy. However, when your glycogen reserves run low, such as when you're in a fasted state, your body turns to fat reserves to fuel your movements.
However, there are some caveats. Your body doesn’t particularly enjoy being deprived of food, and it tends to hold onto fat reserves. When fat is burned rapidly, your metabolism starts to adjust to prevent further loss. Essentially, it enters survival mode, slowing down and burning fewer calories, as Pritchett explains. After burning fat, your body may even store more fat during your next meal, which undoes the benefits of fat burning. A study published in the American Journal of Clinical Nutrition also discovered that prolonged fasting can reduce resting metabolic rates, highlighting that skipping meals for long periods doesn’t offer any true advantages.
Exercise with pre-fueling might even reduce your appetite more effectively than fasted exercise, according to a study published in the journal Appetite. While participants burned the same amount of energy overall, those who ate before working out reported feeling less hungry afterward. Since weight loss largely depends on how you eat, not just exercise, this can be an important factor for anyone working out with the goal of losing weight.
The effects on your muscles
Exercising on an empty stomach may cause you to lose muscle mass along with fat under certain conditions. If your body runs out of glycogen, it may begin to break down muscle proteins for energy, in addition to burning fat. While intense workouts naturally cause some muscle breakdown, doing so while fasted accelerates the process, making it harder to regain the muscle you’ve lost.
However, this effect only happens when you push your workout intensity beyond your typical routine. If you were to engage in a standard workout early in the morning, your muscles would likely have enough glycogen from your previous meal. According to one study from the Journal of Applied Physiology, working out in a fasted state doesn’t affect your physical performance or effort during moderate, submaximal exercise. Whether you’re hungry or not, you can still perform your usual workout at the same intensity without worrying about muscle loss.
Your workout might not be at its best
This leads to another issue, though. While you can manage a fasted workout, you won’t have the energy to push yourself further, making it unlikely that you’ll improve as fast as you would if you had eaten beforehand. A separate study, published in the Journal of Science and Medicine In Sport, shows that fasted training falls short compared to fed training when it comes to high-intensity exercise or setting new personal records. Pushing yourself is key to building muscle mass and improving run times, so it’s important to give it your all. Ultimately, eating before a workout can actually boost your metabolism over time.
In conclusion, working out on an empty stomach is possible and some people prefer it because it makes them feel lighter, more focused, and alert. However, aside from personal preference, there aren’t many advantages. It’s better to consume a carb-rich meal about an hour before your workout, followed by a high-protein, low-carb meal afterward. Plus, skipping meals can leave you in a bad mood. You’re better off finishing your workout feeling refreshed and happy, not miserable and desperate for food.
