Intermittent fasting involves eating only during certain time-restricted periods. And it turns out Ive been doing it practically my whole life.
Heres my confession: I hate breakfast . So when I discovered that skipping it could actually be healthy, it was like I just got permission to do what my body wanted to do anyhowand I ran with it. Literally. Nearly three years ago, I decided to formalize my eating style and embrace intermittent fasting.
While there are lots of different ways to do it the 16:8 diet , OMAD (one meal a day) , the 5:2 diet the basic idea of intermittent fasting is to your limit your eating to a particular window of time. After trying a bunch of different protocols, I finally settled on 18:6, meaning I fast for 18 hours a day and eat during a six-hour window, from 2 to 8 p.m. each day. From an eating standpoint, it was one of the easiest things Ive ever done; Im not usually hungry until about then anyhow.
Yet there was one thing thats always bothered me. How was it affecting my body when it came to exercise? I work out six days a week, doing a mix of cardio, yoga, and weight lifting. My workouts are non-negotiable, as they are essential to dealing with my lifelong depression and anxiety issues. While Ive always felt fine working out in a fasted state , Ive wondered if maybe I was doing some kind of long-term damage and just didnt realize it yet. So I decided to find out.
Can you exercise while intermittent fasting?
The short answer is yes, says Jonathan Poyourow , RD, CSCS, a sports dietitian, professional chef, and associate professor of nutrition at Johnson & Wales University . Do you have to do intermittent fasting to achieve your diet or fitness goals? Absolutely not, Poyourow explains. But if you want to try fasting, there are ways to make it work with your workouts.
The longer answer is that it depends on many factors, including your age, overall health, fitness level, goals, nutrition, and lifestyle.
But if you consider yourself a serious athlete, it might not be the best fit. I do not support combining intermittent fasting and working out, especially for athletes, says Rachel Fine , RD, a registered dietitian nutritionist, a board-certified specialist in sports dietetics, and owner of To The Pointe Nutrition . For people who work out a lot, the goal of a diet should be fueling the body and that can be hard to do with intermittent fasting.
Working out, particularly when you do it almost daily, puts a lot of stress on your physical and metabolic systems and to support your workouts and recover properly you need a certain amount of calories strategically eaten throughout the day, Fine explains.
Ultimately its about whether it fits with your lifestyle and your body, its very individual, Poyourow says, adding that he recommends talking to a doctor before starting any type of fasting plan if you have any health concerns.
Halle Berry swears by a combination of keto and intermittent fasting:
So how should you time exercise while intermittent fasting?
Poyourow recommends timing your fast so your workout happens at the end of it. Is it going to be painful to hit the gym after, say, a 16-hour fast? Yesbut you'll get used to it.
It will likely take a few weeks for your body to adjust and during that time you should take it easy, Poyourow says. But your body can and will adapt after which you should be fine to stick to your regular schedule, even on the days you are fasting.
The important thing to keep in mind for people who do IF and exercise a lot is that you have to keep drinking water, lots of water, Poyourow says. You need to drink one-half to one gallon of water per day and if you sweat a lot, consider adding an electrolyte tablet, he advises.
You might also maximize your weight-loss potential by saving your sweat session for the end of your fast. Studies have shown that it takes a good 10 to 12 hours to burn up your glycogen stores and switch to mainly burning fat, he explains. So working out at the end of your fasting period means youll be using more of your stored fat for energy.
Plus, your muscles will be primed by your workout to better absorb the protein and nutrients from your breaking the fast meal, he adds.
The key is to listen to your body and learn to recognize what is normal you-can-push-through-it pain from working out and what is unusual for you, he says. If it hurts in a bad way, stop doing it.
I usually hit my workouts in the middle or towards the end of my fasting period, mainly for practical purposes. Between being a mom and working full time, I dont have the mental bandwidth to worry about timing everything perfectly, but the slight fluctuations in timing make little difference in how I feel or perform.
But listen, if you feel like breaking your fast with a snack before your workout, it's no big deal, and if it helps you exercise longer and harder then its worth it, Poyourow says.
You have to have enough energy to workout, he explains. Is it even worth working out if youre just dragging through it and feeling miserable?
When it comes to what to eat, Fine says to skip the processed pre-workout drinks, powders and bars and instead recommends a whole-food snack that combines protein and carbs, like a piece of whole grain toast with almond butter.
Can you build muscle while intermittent fasting?
As long as youre getting enough protein and nutrients as part of a healthy, balanced diet overall, then your muscles will be just fine, Poyourow says. Im a girl who lifts and likes to lift heavy so the thought that IF could be stunting my muscle growth was scary to me.
So over the past year I decided to start tracking my body fat percentage and lean muscle massand Ive actually dropped three percent body fat and put on nearly four pounds of muscle. Im just a study of one but for me, my muscles do just fine on IF.
View this post on Instagram For all the people who don't believe me when I say I sweat like a dude... They say everyone has a talent! (And no I'm not lactating. Those marks are from where my soaking wet braid kept smacking me ) A post shared by Charlotte Hilton Andersen (@charlottegfe) on Jul 12, 2018 at 10:18am PDT
What should you eat to break your fast after a workout?
Because youre eating fewer meals, you need to make every meal count nutrition-wise, Poyourow says. This means sticking to whole, unprocessed foods, including meats, vegetables, and fruits. (Hes personally a big fan of the Mediterranean style of eating.) Why undo all your hard work in the gym by eating garbage? he adds.
For recovery and muscle growth, its important to get a mix of protein and carbs within an hour of finishing your workout, Fine explains. She recommends making a smoothie with whole fruit, spinach, yogurt, and nut butter.
She adds that its important to make sure youre eating enough calories to fuel your body and your workouts. How much will depend on a lot of factors, she recommends speaking to a sports dietitian to figure out your bodys requirements.
Will exercising while intermittent fasting help you lose more weight?
Weight loss is the main reason most people try IF, and you might think that adding daily workouts could help you lose weight faster. This type of thinking can backfire, though.
Extra workouts increase your hunger overall, which can make fasting feel harder. Weight loss is all about creating a calorie deficit and pretty much any type of diet will do that if you stick to it, Poyourow explains. You can definitely overeat during your eating window and gain weight, even if youre working out.
I can tell you from first hand experience its plenty easy to eat all my daily calories (and even more, if Im not careful) in just a couple of meals. This isnt a problem for me as weight loss is not my goal; Im already at a healthy weight.
But if weight loss is your goal, youll still need to track what you eat and use portion control, he says. In addition, you might want to rethink the number and intensity of your workouts. Even with IF, you should aim for slow and steady weight loss for it to be sustainable, he says.
If every workout feels miserable, you should stop intermittent fasting.
It takes a few weeks for your body to adjust to any new routine so you cant make a judgement until youve given it at least a couple of weeks, Poyourow says. However, intermittent fasting isnt for everyone. So how do you know if its doing more harm than good?
If youre experiencing mental fog, obsessive thoughts about food or weight, weakness, exhaustion, feelings of depression or burnout, insomnia, stress injuries, extreme muscle soreness and/or very slow recovery after your workouts, then its time to call it quits, Fine says. Intermittent fasting, particularly if youre under-eating, can lead to an increased risk of injury, lowered bone density, and mental illness, she cautions.
There are lots of ways to achieve your health goals and if intermittent fasting isnt helping you reach them then move on and try something else, Poyourow says. Its all about figuring out what works for you and that may not be the same thing that works for someone else.