The New Cardio Question: To Fast or Not To Fast
If you follow me on Instagram (please do: @drmeganbrown), you know I recently went on a Bermuda bender with fellow Stylebook contributor, Chef Nicole. After my trip, I reached out to IG land for clean eating suggestions because I needed to detox! One of my friends, HAWT Pilates instructor and now Physical Therapy Assistant student, Andrea Miller, responded with this suggestion and I posted it:
I had scores of questions about fasted cardio after that post and I had to admit, I didn’t have all the answers. Being curious myself, I decided to do the research.
What is it?
Just as it sounds, you are performing your cardiovascular exercise (cardio) on an empty stomach — preferably after fasting over night. If fitness goals include weight loss, many people use this strategy to burn more body fat.
What’s the theory?
Once you ingest food, insulin is secreted to break down the carbohydrates. It is theorized that insulin inhibits lipolysis. What is lipolysis? The break down of fat molecules for energy. Therefore, if we do our cardio before we eat, our bodies will break down fat instead of carbs, and improve the total fat loss effects of performing cardiovascular exercise. 
What’s the science?
Okay, so this was a bit all over the map. The first studies came out in the 70s, and they supported this theory. More recent studies, including two systematic reviews, pledge for both both sides: some say yes it works, some say there was no difference, each with their own limitations, design, and participants.
Should you do it?
It truly depends on your goals. If your goal is to improve muscle mass and anaerobic capacity (i.e., you’re training for something), then no, don’t do this method. If healthy weight loss is your goal, I say yes and here’s why:I am a fasted cardio subscriber by default because I already practice intermittent fasting (you’ve heard me talk about this on Stylebook here, here, and here). The reason I practice IF is because of my voracious appetite. Yes, I eat a ton of food and can get very “hangry” during the day if I don’t get enough. Eating within an 8-hour window allows me to eat the normal recommended amount of calories without that uncomfortable starved feeling. I swear by it. And so do Beyoncé and J.Lo, by the way.Performing your cardio workout in a fasted state will likely reduce your overall caloric intake if you are trying to lose extra pounds and obtain a healthy weight. For example, if you eat a hearty breakfast before your workout, you will likely eat a hearty lunch, snacks, and dinner. Reducing that first meal to just coffee allows you to stay within a healthy, ideal caloric intake. On some days I take that opportunity to have a big fancy meal, equipped with garlic bread, good wine, and dessert.So even if the science is all over the place (in scientist terms we are supposed to say, “More studies are needed to investigate the effects of fasted cardio versus fed cardio.”) there are definite weight loss benefits to fasted cardio if healthy weight loss is your goal.
How do you do it?
There are some rules surrounding how to do this properly:
- The benefits of fasted cardio are associated with light to moderate exertion steady-state cardiovascular exercise limited to an hour or less (I hear cheering all across the land).
- Exercise in the morning for better results. It is a lot more difficult to fast all day before an evening workout.
- Water is a must and black coffee is allowed beforehand (the caffeine really helps my energy and motivation).
- This fasted workout method does not pertain to weight training.
Overall, and I know we all say this, listen to your body and experiment with what works best for you. If you’d like to practice your fasted cardio with me you can find tons of cardio options at Mind the Mat; look for Pilates Boot Camp and HIIT Pilates Barre. I also offer classes online at www.drmeganbrownPT.com for only $9.99/month, a perfect travel solution to exercising on the go! 