Intermittent fasting continues to be a hot topic in the wellness world, particularly with regards to weight loss and longevity. Chances are you know someone who has tried it, swears by it, or wasn’t into it—maybe even you yourself have given it a go.
The concept of fasting has been around for centuries, and the benefits are relatively well-documented, but there are still concerns around its practicality for runners and endurance athletes. Is it healthy for runners to intermittent fast? Does it improve performance, or hinder it?
If these are questions you have, here’s what you need to know.
What is intermittent fasting?
For anyone unfamiliar with intermittent fasting, it’s a way of eating that involves breaking your day into two parts—your eating window and fasting window. As the names suggest, you fast during your fasting window and eat only during your eating window. The most popular form of IF is the 16:8 method, which means you fast for 16 hours and confine your meals to an eight-hour eating period. Some people take a more aggressive approach, fasting for 18 to 20 hours at a time or fasting for a full 24 hours once or twice a week (referred to as the ‘eat-stop-eat’ method).
The majority of people who engage in intermittent fasting do so for weight loss because many people who do IF eat fewer overall calories than they would without a limited eating window. (In other words, fasting puts them in the caloric deficit they’d need to lose weight.) People also use IF to address other aspects of their health, as studies have shown that fasting can help with insulin resistance, cellular repair, gut health, and inflammation.
Is intermittent fasting good for runners?
While it would be satisfying to give you a straightforward, one size fits all answer, the verdict on whether or not intermittent fasting is healthy for runners depends on several factors: your workout schedule, your intensity/duration, and your body.
Before you decide to try intermittent fasting, it’s important to take a look at your workout schedule, the kinds of runs and workouts you do, and how your body responds to said workouts.
In theory, there are three times of day when you could get a workout in: in the morning, in the afternoon, or at night. People who work out in the morning may have a tough time reaching peak (or even moderate) performance, especially if the run they’re doing is either high intensity or long in duration. This is because your body is in a fasted state, and you lack the energy you’d need to fuel the workout—energy that comes from food.
The same can be said for people who work out at night. Your body may be tired at the end of the day, and, depending on when your eating window ends, you could experience exhaustion and fatigue that could compromise your workout.
In reality, the runners who are best suited for IF are those that run in the afternoon, because the run occurs after they’ve eaten in the morning and they’re able to replenish their energy stores afterward. Of course, for those who have jobs, families, or other obligations, running midday can be impractical. Also, in warmer months, the afternoon heat can be unbearable for runners (and fasting runners). So, even this has its drawbacks.
In addition to the time of day, the intensity and duration of your workouts will make a major difference in your ability to intermittently fast. If your workouts are on the shorter side, you may get through them and feel fine. Longer workouts, though, require proper nutrition. Doing them in a fasted state causes undue stress on the body, which often leads to injury and even loss of consciousness (aka passing out). Bottom line: Shorter, easier workouts can be done whilst in a fasted state, and longer and/or high-intensity workouts cannot.
P.S. If you aren’t sure what to eat before or after your runs, don’t worry, we’ve got you covered.
The final word
For anyone who is hellbent on trying intermittent fasting, we recommend treating it as an experiment and starting slow. We don’t recommend starting IF while you’re training for a race or endurance event, but if you’re in the offseason and want to try it out, there isn’t a major risk or ill fate associated with doing so. Above all, listen to your body and tune in to what it needs. Depriving yourself of food when you need it will always backfire, and no amount of weight loss or performance gains will change that.
Please note: This blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.