Can you exercise when you fast

The short answer is yes! Exercising in a fasted state will result in burning glycogen stores, which is a really effective way to lose weight and lean out. However, there are a few things to keep in mind when you exercise in a fasted state, which I cover here. 

Fasted exercise for weight loss

When you exercise in the morning in a fasted state, your blood sugar is likely already at its lowest. Low blood sugar means that you don’t have glucose readily available for energy and your body will have to look elsewhere for an energy source. This is a good thing. Without glucose available, your body will start to go after something called glycogen

Glycogen is sugar that your body has stored in your liver, fat and skeletal muscle. Burning these accumulated sugar stores is often the missing link to many peoples weight loss success. So if weight loss is your goal, exercising in a fasted state can be helpful. 

Let’s consider what happens if you have a protein shake before you work out. A protein shake will provide your body with immediate and readily available sugar for energy. Your glucose levels will rise upon consuming the shake, and when you exercise your body will use this glucose for energy, and will never get to the stored glycogen.

Supplement with minerals

The one caveat to exercising in a fasted state is minding your mineral balance. Fasting can sometimes cause a depletion of essential minerals such as sodium, potassium and magnesium. This is what often causes fasting related headaches and fatigue. So if you are going to exercise in a fasted state, I recommend keeping your mineral intake up. I like using LMNT packets, which come in easy single serving packets and will not break your fast. 

Also note that I do NOT recommend working out in a fasted state if you are in a longer fast, such as a 3-5 day water fast. This creates too much hermetic stress on the body, as your body is already working hard on repair, regeneration and healing. 

Fasted exercise for muscle building

The best way to build muscle is through a process called metabolic switching. This means switching between being a state of sugar burning and fat burning (ie. ketosis). By the way, metabolic flexibility is not just helpful for building muscle, but creating long-term health and your best defense against viruses like COVID-19.

When we practice this concept in my Reset Academy, I teach clients how to build muscle by switching between autophagy fasting and intermittent fasting. During autophagy days you will be fasting for 17 hours, keeping protein under 20g, carbs under 50g, and sticking with a light workout. 

Following an autophagy day, you’ll do a protein building day. During a protein building day you will stick to intermittent fasting, 13-15 hours at most. You will consume 20g of protein every couple hours, up to 150g of protein and 75g of net carbs, which will stimulate mTor, a naturally-occurring substance that regulates muscle growth. Protein building days are when you will want to do your heavy workouts and strength training, in a fasted state. 

Download the Muscle Reset Guide HERE!

How do you break your fasted workout

Immediately following your fasted workout, try eating protein only. Yes, this means no fat and no carbs. Again, this is intended to maximize mTor. Some of my favorite ways to do this is with grass fed beef or PaleoValley Beef Sticks.

Example of a weekly muscle building protocol

YouTube link 


One Comment

  1. April O March 22, 2021 at 4:12 am - Reply

    I’m a bit confused. The graphic shows M-F autophagy then protein loading the day before and after your heavy workout… This assumes you only workout once a week, But what if I’m working out fasted MWF mornings, strength training. Would i protein load literally every day?

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