Fasted vs. Fueled Exercise: What's Right for You?

What should you do? Eat or not eat?

Have you ever wondered whether you should eat something before your workout or start exercising without eating? It’s a common question many people face every day. The choice you are making involves exercising fasted or non-fasted. Fasted exercise involves working out on an empty stomach (typically at least 8 hours) and non-fasted exercise involves consuming some form of calories before a workout.

Research has shown that fasted exercise alters physiological processes, such as increasing lipid oxidation during low-intensity endurance training. Your glycogen stores also become depleted much more quickly during fasted exercise, which in turn causes the body to turn to fat to burn for energy. However, research has yet to translate this increase in lipid oxidation into improvements in performance or faster weight loss. Additionally, there is disputing evidence on fasted exercise causing an increase in breakdown of muscle or impacting hormonal balance, especially in females. Ultimately, research shows no difference between body composition in individuals who train fasted vs non-fasted.

So, what should you do? Eat or not eat?

Instances where it is appropriate to train fasted:

  • Workouts under 1 hour in duration

  • Lower intensity workouts, like jogging, walking, or cycling, where heart rate stays at or below 50-60% of maximum capacity

  • Workouts in which performance is not your main focus

If you do decide to go into a workout fasted, it is crucial to fuel within 30 minutes after the workout for proper recovery. This recovery meal should include protein, carbohydrates, and fat. The protein will help repair damaged muscle tissue, the carbohydrates will provide energy and replenish carbohydrate stores in your muscles, and the fat will add additional energy as well as support absorption of certain nutrients. Examples include:

  • Morning recovery meal: scrambled eggs with avocado, toast, and blueberries

  • Evening recovery meal: grilled chicken breast, corn, brown rice, and olive oil

Now that you’ve learned about fasted exercise, it’s important to understand the benefits of fueled (non-fasted) exercise.

  • Enhanced energy levels: Consuming a pre-workout meal or snack consisting of carbohydrates will provide the body with energy to fuel a workout. This is especially important for longer duration workouts and higher intensity workouts.

  • Muscle preservation: Having adequate carbohydrates available to serve as fuel will prevent breakdown of lean tissue, like muscles, for energy.

  • Improved endurance and performance: Being properly fueled will allow you to train for longer durations and optimize your performance. This is crucial when training for a race, such as triathlon or marathon that involves high volume endurance training.

Here are some pre-workout snack ideas to help fuel your workouts. These pre-workout snacks should consist primarily of carbohydrates that are low in fiber.

  • Granola or cereal

  • Clif Bar

  • Banana or dried fruit

  • English muffin or bagel with peanut butter, honey, and/or jelly

If you are someone that struggles with GI discomfort or nausea when eating before a workout, try liquid carbohydrate sources, such as sports drinks. These tend to be digested and absorbed more rapidly.

The choice between fasted and fueled exercise ultimately depends on your personal preferences, fitness/performance goals, and how your body responds to each approach. If your primary aim is fat loss, fasted workouts may be appropriate (but still, as mentioned above, not always). However, if your primary goal is to optimize your performance or gain muscle, make sure to fuel your training sessions appropriately!

Health Wellness, Weight Management, Performance, Muscle GainBethany Villarreal