"COVID-19 Update: I am excited to announce that In-Home Training is once again available. To allow for safe In-Home Sessions, strict guidelines will be followed; to view those guidelines please read COVID-19 Update: In-Home Training . Virtual Training and Online Training are also available. For now Training at Fortis Fitness West is still suspended."

Is Fasted Cardio better for Fat Loss?

Author: Train Smart Fitness & Health | | Categories: Fitness Instructor , Health Improvement Programs , In-Home Personal Trainer , Kinesiologist , Online Personal Training , Personal Fitness Trainer , Personal Trainer , Private Training , Wellness Programs


A very common piece of advice given for fat loss is to do your cardio first thing in the morning, before any meals, as this will lead to greater fat loss than performing cardio after a meal. But is this true? Does Fasted Cardio result in greater fat loss?

The reasoning behind this belief is that when you wake up, since you haven’t eaten anything since the night before, you are in a fasted state and your glucose levels will be lower. This is true. So, by then performing a Cardio workout your body won’t have as much Glucose to draw from for that exercise, so instead it will preferentially use Fat as the fuel source. There is research to support this.

What the Science says

In a 1976 study Ahlborg & Felig (1), looked at the effect consuming Glucose would have on Fat and Glucose utilization by the body. Their subjects consisted of 6 healthy males, who after a 12-14hr overnight fast, performed 4hrs of cycling at a low intensity. 90min into the exercise they ingested 200g of Glucose while continuing to exercise.

Yuck, those Glucose drinks taste awful by the way.

They compared this to a control group who did the same exercise, but without the Glucose drink. What they found was that up until 90min both groups were using increasing amounts of Fat to fuel their exercise. However after the Glucose group ingested the Glucose, they started using more Glucose and less Fat.

What this suggests is that consuming Glucose will lower the amount of Fat used for the exercise.

So case closed. Don’t eat before your morning Cardio and you’ll burn more Fat during the Session.

Plot twist!

You already know that to lose weight or Fat, you need to look at your overall daily energy balance and create a calorie-deficit; using more calories than you’re taking in.

If we’re using Cardio to create a 500 calorie-deficit does it really matter whether you perform that Cardio while fasted versus later in the day when you’re fed?

In 2014, Schoenfeld et al. (2) looked at answering that question.

They performed a study with 20 healthy young females, they tested their Body Mass and Body Composition; the percentage of Fat Mass and Fat-Free Mass, and Waist Circumference. They were then put on a Hypocaloric diet (in this case, 500 Calories below their Maintenance Calories) with a similar macronutrient breakdown for 4 weeks and also performed 1 hour of supervised Steady-State Cardio 3x per week on a Treadmill. They used a low-moderate intensity as this has been shown to maximize the use of Fats while performing Fasted Cardio. Those 20 participants were split into 2 groups, one group performed the Cardio while Fasted after which they received a meal replacement shake and the other group performed the Cardio after consuming the same shake.

After the 4 weeks, they measured their Body Composition again and found that both groups lost a similar amount of total Body Weight and Fat Mass. Being in a Fasted state did not give them a benefit.

Why is it so popular?

This begs the question, why are people seeing such good results with Fasted Cardio? It’s helped me, it might have helped you. Your shredded buddy at work swears by it. That trainer you met at the gym recommends it.

More than likely it's coming down to a matter of proper implementation. Most people suck at tracking, both their diet and their activity. Someone might say they do 30min of Cardio 3x a week in the evening after their lifting session, but if you were watching them; you would probably find that they’re really only doing 20min if at all. After a long day of work, errands, family obligations who really wants to spend 30min on the Rower, Treadmill or Elliptical doing Cardio.

So, Fasted Cardio enters the picture. You wake up a little bit earlier, you’re kids are probably still asleep, you haven’t been bothered by work yet. The usual distractions and fatigue from the day haven’t set in yet; your world is just...quite. You lace up your shoes and get in your 30min before your usual day starts. You do this a few times a week for a month. And...wow you’re seeing good results.

What are the real differences between your evening Cardio and morning Cardio?

  1. You’re not distracted by competing priorities
  2. You’re not shorting yourself on the session length or intensity
  3. You’re probably just being more consistent with it.

Real-World Application

When you choose to do your Cardio is not that important. For the average person, doing your Cardio while Fasted or Fed, when paired with a good, lower-calorie diet, gives you the same outcome. In other words (Just Do IT).

If you like doing your Cardio while Fasted, then keep going. If you like doing your Cardio after a meal, then keep going. If you’re confused about the “when”, ask yourself these questions:

  1. What time of day do I have the least amount of distractions?
  2. Do I have enough time in the evening/afternoon to get in a Cardio session?
  3. Can I wake up earlier?
  4. If I wake up earlier, will I do the full Cardio session I had planned?
  5. Will it impact my Resistance Training Session?

Before the Fasted Cardio fanatics come after me, If you feel you’re getting some other benefits from it like better mood, mental clarity or find it to be the holy grail of staying shredded year-round. If it’s working for you or your clients, keep doing it.

When I used to do Fasted Cardio, for me it was a mental win. Accomplishing something first thing in the morning motivated me and gave me momentum in the right direction. At some point I’ll probably start doing Fasted Cardio again.

To sum this all up. Yes, Fasted Cardio burns more Fat DURING the session, but it doesn’t lead to better Fat Loss compared to Fed Cardio. The “when” isn’t all that important, compared to actually doing it and doing it consistently.


  1. Ahlborg, G., & Felig, P. (1976). Influence of glucose ingestion on fuel-hormone response during prolonged exercise. Journal of Applied Physiology, 41(5), 683-688. doi:10.1152/jappl.1976.41.5.683
  2. Schoenfeld, B. J., Aragon, A. A., Wilborn, C. D., Krieger, J. W., & Sonmez, G. T. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. Journal of the International Society of Sports Nutrition, 11(1). doi:10.1186/s12970-014-0054-7