Is Fasted Cardio in the Morning Effective? Here’s What the Experts Say

Experts believe fasted cardio in the morning can be effective for burning body fat. When exercising without recent food intake, your body taps into stored fat as its primary fuel source, potentially leading to increased fat loss.

As a personal trainer, I constantly get asked if working out first thing in the morning on an empty stomach can speed up weight loss. Proponents of fasted cardio claim it melts fat off like magic, whereas skeptics argue it can burn muscle and lower energy reserves.

I spent over 50 hours researching fasted cardio in the morning to bring you the most up-to-date and reliable answers.

A review published in the Scandinavian Journal of Medicine and Science in Sports noted a possible small increase in fat burning during fasted cardio. However, overall weight loss over time might not differ significantly from fed-state cardio. (1)

While fat oxidation plays a crucial role in weight loss, it’s not the whole story. Weight loss ultimately boils down to calories in versus calories out. You must enter a calorie deficit to lose weight, meaning you must burn more calories daily than you consume.

A heightened fat oxidation means your body is burning more fat for fuel, leading to an increase in fat loss. However, overall weight loss can occur from the loss of fat, muscle, and water.

While fasted cardio in the morning can boost fat oxidation, you must combine increased fat oxidation and a daily calorie deficit to lose weight sustainably. (2)

Benefits of Fasted Cardio in the Morning

Here are the advantages of doing cardio on an empty stomach:

Increased Fat Burning

When you don’t eat anything overnight, your body is running low on glycogen stores. This forces your body to dive into the fat stores for fuel, leading to greater fat oxidation. Think of it as shifting your metabolism into a higher fat-burning gear.

Improved Insulin Sensitivity

Insulin shuttles sugar out of the blood and into the tissues. Excessive insulin levels can sabotage fat loss. A review published in the Sports Medicine journal found that fasted cardio can boost insulin sensitivity over time, which can make your body better at utilizing insulin and boosting fat burning. (4)

Boosted Metabolism

Some experts believe that cardio on an empty stomach can boost your metabolism, which can help you burn more calories throughout the day. However, its absolute effects on weight loss are likely marginal.

Drawbacks of Fasted Cardio

Before you start fasted cardio in the morning, you must know about its potential cons:

Reduced Performance

Many of my personal training clients report feeling lethargic while training on an empty stomach. The higher your training intensity and the longer your session, the more energy you need. I recommend elite athletes train after eating a balanced pre-workout meal to ensure optimal glycogen levels.

Muscle Breakdown

Training on an empty stomach can put you in a catabolic state, where your body burns muscle tissue for energy. This is counterproductive for people aiming to promote hypertrophy.

Sustainability Issues

Let’s be honest: fasted cardio is not sustainable for most people. If you aim to lose weight but cannot stick to the fasted cardio for the long term, it is not ideal for you. Furthermore, if your training sessions make you feel miserable, you’re less likely to maintain it for the long term.

Inconsistent Results

Most people associate fasted cardio with intermittent fasting, which involves cycling between periods of voluntary fasting and eating. The length of the fasting window can vary for each individual. For instance, people who eat dinner before 8 p.m. and train at 8 a.m. the next day will have fasted longer than those who eat dinner at 9 p.m. or later.

Before you begin your fasted cardio program, you must define the duration of the fast. The fasts must suit your lifestyle to ensure long-term adherence.

Increased Cholesterol Levels

A study published in the Frontiers in Endocrinology journal found that skipping breakfast can lead to a decrease in body weight but also an increase in bad cholesterol levels. It added that “skipping breakfast might be an alternative way to lose weight, but it is a bad idea because of its negative effects on some cardiovascular risk factors.” (3)

Is Fasted Cardio in the Morning Effective: What Do The Experts Say?

The fitness world is split on the benefits and effects of fasted cardio.

Training on an empty stomach is a hit with competitive bodybuilders, especially as they begin shedding excess body fat to reveal muscle condition as they near a contest.

“Fasted cardio worked really well for me when I was getting ready for competitions. It helps burn fat a lot more efficiently and effectively than just doing cardio any time of the day,” said three-time Mr. Olympia silver medalist (1986-88) Rich Gaspari, who set new standards for muscle conditioning in competitive bodybuilding. 

However, not everyone is as enthusiastic about fasted cardio as Gaspari. Exercise scientist Dr. Mike Israetel (Ph.D. in Sports Physiology) believes performing a cardio session fasted or after eating has insignificant differences. The most significant factor for weight loss is burning extra calories and hitting the target deficit for your objectives.

“Cardio isn’t this magic thing that burns tons of fat. What it really does is it takes your overall calorie deficit and sinks it lower,” said Israetel.

Dr. Layne Norton (Ph.D. in Nutritional Sciences) highlights the effects of fasted cardio on the metabolic rate and how it might not be the best tool for weight loss.

“Fasted cardio does not necessarily lead to more fat loss because the body compensates for the reduced calorie intake by lowering energy expenditure. This aligns with other studies that show no difference in fat loss between fasted exercise and fed exercise when calories are controlled,” said Dr. Layne Norton.

Although fasted cardio is fast gaining traction, not much is said about what to do once your training session is over. Dr. Rhonda Patrick (Ph.D. in Biomedical Science) weighed in on the subject:

“Training fasted shouldn’t have a dramatic effect on cardio or weight training. However, if you are doing fasted workouts, you may want to consume protein within an hour after since you aren’t storing proteins in a fasted state.” — Dr. Rhonda Patrick

Dr. Andrew Huberman (professor of neurobiology and ophthalmology at Stanford University) recommends an alternate method for people who cannot train on an empty stomach:

“Fasting before high-intensity training can help increase the percentage of body fat burned during exercise. However, if you’re unable to train without eating, then it’s best to choose a pre-workout meal that helps keep insulin levels low.” — Andrew Huberman

Should You Do Fasted Cardio?

Whether fasted cardio in the morning is right for you depends on multiple factors, including:

• Fitness Goals: People trying to lose weight using low to moderate-intensity short cardio workouts might find success with fasted training. However, people training for marathons must fuel up before training.
• Experience Level: Fasted cardio training can be intimidating for beginners. Empty stomach training is best reserved for more experienced trainers.
• Body’s Signals: You must learn to listen to your body. While some people thrive on fast workouts, others might feel dizzy and nauseous. Experiment with fasted cardio in the morning to determine how your body performs.

Fasted cardio can be incredibly effective for people who are already pretty active and want to boost their fat-burning even further.

You must start slow and increase the fasted cardio duration as your body gets used to your workout regime. I recommend starting with a 10-minute low-intensity steady-state fasted cardio session and slowly increasing the time.

Many people abstain from drinking water for a fasted cardio session. However, this significantly increases dehydration risk, which could lead to several health issues like dizziness, fast heart rate, and low blood pressure. Make sure you are drinking ample water before, during, and after your training session to prevent electrolyte imbalance.

While fasted cardio can be a potent weight loss tool, you don’t need to do it all the time. Following a balanced diet and exercise regimen and maintaining a healthy calorie deficit can help you achieve your weight loss goals.

Conclusion

While fasted cardio in the morning can lead to an increase in fat oxidation (burning more fat stores due to a lack of glycogen), studies show there is no significant difference in weight loss between people who did fasted cardio and those who exercised after eating. You can combine a higher fat oxidation through fasted cardio and a calorie deficit to shed the spare tire.

I highly recommend sticking to an exercise and diet regime that fits your lifestyle to ensure long-term success. Adopting an early morning fasted cardio session can spell disaster for people who have a hard time getting up in the morning and starve throughout the workout.

If you have any questions about fasted cardio and weight loss, drop them in the comments below, and I’ll be happy to help!

References

1. Aird, T. P., Davies, R. W., & Carson, B. P. (2018). Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis. Scandinavian journal of medicine & science in sports, 28(5), 1476–1493. https://doi.org/10.1111/sms.13054
2. Vieira, A. F., Costa, R. R., Macedo, R. C., Coconcelli, L., & Kruel, L. F. (2016). Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis. The British journal of nutrition, 116(7), 1153–1164. https://doi.org/10.1017/S0007114516003160
3. Yu J, Xia J, Xu D, et al. Effect of skipping breakfast on cardiovascular risk factors: a grade-assessed systematic review and meta-analysis of randomized controlled trials and prospective cohort studies. Front Endocrinol (Lausanne). 2023;14:1256899. Published 2023 Nov 28. doi:10.3389/fendo.2023.1256899
4. Hansen, D., De Strijcker, D., & Calders, P. (2017). Impact of Endurance Exercise Training in the Fasted State on Muscle Biochemistry and Metabolism in Healthy Subjects: Can These Effects be of Particular Clinical Benefit to Type 2 Diabetes Mellitus and Insulin-Resistant Patients?. Sports medicine (Auckland, N.Z.), 47(3), 415–428. https://doi.org/10.1007/s40279-016-0594-x

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