Intermittent Fasting & Working Out in 2020

“Running on Empty”, by Jackson Browne isn’t just a great song it’s at the heart of a huge debate within the fitness and health community. I’m talking about the debate as to the health benefits that working out while not eating or fasting can have on your body and your fitness goals. For those using intermittent fasting to reach their weight loss goals, this is of serious concern. We are going to walk through the pros and the cons of this fascinating topic and hopefully give you some science backed tools to formulate a plan of attack. 

Food is the gasoline of the engine that is your amazing body… we have all heard this and it’s the truth so why are we even talking about this issue. Well, as with many things in life – the actual facts of the case are complex. When you are intermittent fasting, you are not eating 14-18hr each day or in some cases not eating for 24hr intervals several times a week. We all know you need to be working out in order to achieve your weight loss goals but more importantly for your health and to live a long life. So, you’ll be looking to incorporate working out into your intermittent fasting routine at some point. The key is timing… when and how do we work, working out into the over all plan. 


One study from the British Journal of Nutrition found that men that ran before eating breakfast burned up to 20% more fat than those that ate breakfast and then ran. Hey, that sounds good… let’s all do that. Case closed! Well, not so fast there Action Jackson – on the other side of the coin we see that the Pennington Biomedical Research Center ran a study on a group of men and woman. They fasted every other day for 22 days and their resting metabolism dropped by 5%. Your resting metabolism is how many calories you burn while you are just living your everyday life… the key to long term weight loss is to find ways to increase your resting metabolism. Ok, ok we are halfway into our article here and still no closer to the truth – what’s going on. The truth is that it’s a coin-toss as to which school of thought you adhere to and what you think is truth. I’ve looked at the data and the research and trust me about every time you think you have it nailed down a new study comes out proving the opposite. So, what can we do – one thing that health and fitness experts do agree on is there are a few steps that you can take that will insure not only safe exercise while intermittent fasting but things that will increase your benefits while doing so. 

Is Intermittent Fasting Safe While Doing Cardio Workouts?

Yes, it is however you want to keep your intensity low if you have been fasting. Let’s say have been fasting since dinner and now it’s morning so you are ready for your 5-mile high intensity run. Whoa there turbo, since your body doesn’t have any stored up carbohydrates to burn off, remember you haven’t eaten for 16+hours now, you’ll want to dial the cardio back to a short and easy jog or walk. Using the breathing method is a good gauge of how hard you are working out; you should be able to carry on a conversation pretty easily while working out if you are in that mid-range of energy exertion. 

HIIT or Lifting Weights

For the high-intensity workouts like HIIT Training or lifting weights while intermittent fasting you just need to do those sorts of plans after you have eaten. Pretty simple really, switch that cross-fit class from 6am to say during your lunch break or after dinner when your body is property fueled up with lots of protein and carbohydrates. Remember this, when you do high-intensity training and you don’t have enough fuel in your body, your body starts to break down fat (this is good) but it also starts to break down protein (this is bad!). When your body breaks down protein it’s starting to eat its own muscle and the less muscle you have the lower your resting metabolism and the harder time you’ll have keeping at your healthy ideal weight. 


Ok, speaking of protein now is great time to talk about another point that is key to the intermittent fasting lifestyle. You need to be feeding yourself with loads of high-quality protein sources like fish, chicken and lean red meat. If you are going to be working out while intermittent fasting you need extra protein in order to keep your body building muscle and not trying to eat it, remember… that’s bad. The Academy of Nutrition and Dietetics says that you need about 30g of protein every 4-hours that you are awake. In order to get the most out of your workouts you need to be hitting those protein goals so you might want to consider a high-quality protein supplement shake if you are having a hard time hitting those numbers with food alone. The timing of this protein is key, sandwich your workouts right in-between meals if you can or at least snacks that consist of protein. This might look like having a protein shake before your workout and then post-workout having your main meal of the day to gorge your body with the protein and carbohydrates it needs to start building more lean muscle. 


Don’t snack or you’ll ruin your appetite, remember mom telling you that?! Turns out you are going to have to disappoint mom if you want to intermittent fast and workout. Snacks are key to keeping your body running at peak performance. Now, I didn’t say to load up on the sugary and salty snacks; you need to be keeping your snacking clean and nutritious as well to make this all work right. Something that works great for me is I’ll add in 1 or 2 snacks a day around workouts or cardio sessions of some whole-wheat toast with a few tablespoons of almond butter and a sliced banana. This one snack can easily add in 15-20g of protein and some great carbohydrates to power up the workout and feed the machine to help increase your resting metabolism 

If you are trying to keep yourself from snacking while fasting, check out this supplement: inmitfasting.com

There you have it, some simple and easy tricks to keep your body running at peak performance all while intermittent fasting and working out at the same time. Use good judgement and save those extra hard workouts for times when you have enough food to power through. Use your fasted times to enjoy playing with the family outside or an easy walk around the block … follow those rules and you’ll be shedding pounds and living a healthier and longer life on this intermittent fasting adventure. Till next time!