Now that you’ve got the fasting thing down, you’re probably feeling like a bit of a clever-clogs. So, we’re going to throw you a curve-ball: exercise. And should you exercise while fasting?
Fasting is powerful, but when you combine it with a small amount of moderate exercise? Fahggettaboudit! Whether you choose to dance, strut, spin, jump, run or walk, exercise while fasting doubles down on your fat burning power. Dr. Krista Varady Ph.D., our superstar scientist, talks us through exercise while fasting.
Should we exercise while fasting?
I am often asked if it’s possible to exercise while fasting. When I first started doing research in this field, to be completely honest, I had no idea if exercising while fasting was possible. I assumed that people would feel exhausted and irritable on the fast day, and that they would have no desire to workout. To my surprise, this wasn’t the case at all!
Energy for exercise while fasting
As an aside, I should mention that most people actually report having a boost of energy on the fast day. (At this stage, this is also only anecdotal evidence, but we will be measuring this in an upcoming trial!) And lots of people say they have more of a desire to exercise on the fast day than they do on the feast day. I was shocked. However, I should point out that this boost in energy doesn’t happen right away. It takes most people about 10 days to get used to fasting regimens, and the new ‘up/down’ pattern of eating. The first 10 days can be rough for some people. But if you stick through it and get past this hump, I can guarantee that it will get easier. And after your body adjusts, you’ll also notice that you feel less sluggish and more motivated to be active on fast days. It’s really incredible.
What does science day about fasting and exercise?
Nevertheless, I’m sure you’re probably asking yourself: But will I really have the motivation and energy to exercise while fasting? This seems crazy! To answer this question, my lab group recently performed a study to see if people could participate in an exercise regimen while fasting. The subjects consumed roughly 500 calories on alternating fast days, and also worked out on elliptical machines or stationary bikes three times per week for 45 minutes per session.
We were primarily interested in seeing if people would choose, on their own accord, to exercise while fasting. To our surprise, our participants weren’t weary of exercising on fast days at all! They chose to work on fast days just as often as they chose to workout feast days. 50% of participants reported preferring exercising on the fast day versus the feast day.
In speaking with the subjects, I also learned that many people found that exercising on the fast day was quite easy and that the workout helped to further boost their energy. Once again, I was amazed.
Should you eat before or after?
Additionally, we also wanted to understand if the timing of the fast day meal (before or after the exercise session) would affect one’s ability to stick to the diet. Interestingly, we noticed that the participants who did not eat before working out were less likely to cheat on the diet. 10% of people who saved the fast-day meal for after workout cheated on their diet versus 17% who ate the meal before their workout.
Wait, what? Let me put this in a different way. Most people become extremely hungry about 30–40 minutes after exercising. If you save your fast day meal for after your session, you will be able satisfy your hunger without cheating on the diet. However, if you eat your fast day meal before exercising, there’s a pretty good chance you will be so hungry after your workout that you may cheat on the diet and eat extra calories.
So, in general, don’t be scared of being active on the fast day – there’s a pretty good chance you’ll enjoy it! Just make sure to save that fast day meal for post-workout so you don’t derail your diet.
Interested in the study? Read more here!