Fasted Workout Mistakes to Avoid

Lori Russell, MS RD CSSD
by Lori Russell, MS RD CSSD
Share it:
Fasted Workout Mistakes to Avoid

You’ve likely wondered whether or not you should eat before exercising first thing in the morning, and if there are notable benefits to doing “fasted” workouts. If your reason for avoiding a pre-workout bite is you’re waking up early and don’t have time, or you want to avoid gastric upset during the workout, the process is easy; simply skip eating. However, if you are trying to reap the supposed benefits of fasted workouts, there is much more to it than forgoing the food.

In addition, many who work out on empty might be more tempted to consume extra food or prone to experiencing feelings of ‘I’ve earned this’ later, in turn overcompensating for the additional burn.

Following incorrect protocol when it comes to this practice can have negligible or even dangerous results to your health and performance. Here are some common issues and how to correct them.


There is a physiological difference between not eating and fasting. Technically, fasting should be more than 10 hours — with 12 being more of a ‘magic number.’ This amount of time is what your body needs to fully digest and process the food you’ve consumed and stop relying on glucose for fuel. The ‘switching over’ from utilizing glucose (carbohydrates) to fat as fuel is the main reason for practicing fasted workouts.

For example, many people have dinner at 8 p.m. or a 10 p.m. snack and then do a 6 a.m. workout without eating first. This is not a fasted workout. To reap the benefit of fasting and utilizing fat as fuel, aim to eat meals earlier in the evening or practice time-restricted eating to fully be in a fasted state going into your workout.


Research has shown that after a fasted workout session, fat burning is elevated for 24 hours. However, 24 hours of a slight increase in fat burning might not make a large dent in long-term fat-loss results. Those practicing fasted morning workouts most days of the week might see this additional burn accumulate enough to be beneficial for improving body composition. Those doing it just once or twice a week aren’t likely to dig themselves into a beneficial deficit.

The fat-burning zone during exercise occurs at a low level of intensity. Basically, one can burn a higher percentage of calories from fat by working out slow and long, but working out more intensely can burn more total calories and lead to more total fat calories being torched in the end.

Instead of relying on consistently doing fasted or low-intensity workouts to get lean, try eating a balanced and high-quality diet while doing a mix of high- and low-intensity workouts.


Expecting great performances is a huge reason to partake in fasted workouts. However, going into a workout without fuel puts your body at a disadvantage. The ability to perform at a high level comes from having an immediate supply of carbohydrates and thus glucose, as this is the easiest and fastest way to produce ATP to energize your workouts.

Athletes should expect fasted training to have a higher perceived effort level than the same training done in a fed state. Pushing too hard to hit high numbers in a fasted session can have dangerous results of being dizzy, weak and increasing the risk of injury and overtraining. Fasted sessions provide physiological adaptations that happen over time and benefit future sessions, but won’t immediately provide optimal performances. To prevent hurting your future performances, take the fasted training easier and feed your hard/key sessions.


Remember fasted workouts are a specific type of training that needs extra attention and care to adhere to its protocol. If done correctly, this training can have well-studied, long-term benefits including improving muscle oxidative capacity and blood glucose stability. However, neglecting to follow a well-defined fasting practice while listening to one’s body, can lead to lower energy levels, decreased body composition improvements and potential for poor performance.

Contact an experienced sports dietitian to work with you to define a plan that suits your body and athletic goals.

About the Author

Lori Russell, MS RD CSSD
Lori Russell, MS RD CSSD

Lori, MS RD CSSD is an accomplished sports dietitian; she holds a Master’s Degree in Human Nutrition and Certification as a Specialist in Sports Nutrition. As a current professional road cyclist and previous elite marathoner and ultra-runner, Lori knows firsthand that food can enhance or diminish performance gains. She understands the importance of balancing a quality whole food based diet with science-backed performance nutrition and strives to share this message with others. Learn more about her @HungryForResults.


Never Miss a Post!

Turn on MyFitnessPal desktop notifications and stay up to date on the latest health and fitness advice.


Click the 'Allow' Button Above


You're all set.