Sport Nutrition

Could Intermittent Fasting Unlock Your Athletic Performance Potential?

Intermittent fasting (IF) has quickly become one of the most popular dietary trends of our modern age. I don’t think I meet many new clients these days who haven’t given IF a try, or are at least curious about it! But with all the supposed benefits we read every day online, is it a worthwhile strategy for athletes? Will incorporating intermittent fasting into your nutrition strategy unlock your peak athletic performance?

The idea of fasting in and of itself is really nothing new. Many cultures and religious groups around the world have used fasting for generations as a means to connect with a higher power, or commemorate a historic event within their community. Fasting is often viewed as something that is ‘cleansing’ and good for the body, mind, and spirit. More recently though fasting has caught the attention of some new groups of people. Scientific researchers who want to learn more about the physiological impacts of fasting on our health and longevity, and of course people who want to profit from it. Intermittent fasting as a “diet” has been touted as a cure-all for everything from weight loss, type 2 diabetes management, even as a cure for cancer. According to some of these folks, with intermittent fasting we can live longer and free from disease. All we have to do is start skipping breakfast.

But what about intermittent fasting for athletes?

Athletes tend to be individuals who prioritize good health, so the promises that IF makes can be very appealing, even outside the realm of better athletic performance. I mean who doesn’t want to reverse aging, prevent cancer, and live longer? Shut up and take my money, right?

So, what’s really going on while we’re fasting?

When it comes to intermittent fasting, there’s really two different potential mechanisms at play. The first is that people can lose weight while intermittent fasting because they’re creating a calorie deficit. What this means is that they’ve reduced the total calories they’re taking in each day (by skipping one or more of their meals), and this creates a calorie deficit which results in weight loss. From that we can see improvements in health markers like blood pressure, diabetes control, or heart disease. Some people find this to be an easier calorie reduction strategy than say, trying to stick to a low-carb or low-fat diet (which in theory would provide the same results so long as the same calorie deficit was maintained on each diet) Nutrition research strongly supports this idea – weight loss comes from a simple reduction in calorie intake, there’s nothing magic about it. What may vary from person to person though is the strategy they personally find the easiest to stick with long-term, which is what will produce the results they’re looking for. The human body is complicated, and things like hormones, metabolic rate, hunger, and satiety are all a part of this system, but at the end of the day weight loss does require a change in this total energy balance.

Now the other aspect of intermittent fasting that is gaining major traction is something called ‘autophagy’. This is the thing that has longevity researchers, biohackers, and health-minded folks absolutely enamored, and is more of a draw for many athletes than the potential weight impacts. Autophagy is a process that takes in place within our body’s cell where dysfunctional, damaged, or unnecessary cell components are recycled or removed as waste. You can see why this would spark all kinds of ideas about reversing aging or preventing different types of cancers. Autophagy though is a delicate balance (like everything in the body!) where we definitely want these processes to take place when appropriate, but too much or too little can be harmful to our health. More autophagy is not always better! At this point from a research perspective there are more questions than answers out there, and research in athletes specifically is even more sparse. Studies really tend to focus on things like body composition changes, and often don’t explore IF’s impacts in the context of a larger picture of athletic performance; which includes far more than just an athlete’s weight or body fat percentage.

So sure, incorporating IF into your nutrition strategy may lead to weight loss (like I described above), but depending on your sport a lower body weight doesn’t necessarily translate into better performance.

With that, fasting has come front and centre as something we can do that promotes and speeds up the autophagy process, but the challenge with really discussing IF for athletes is that there’s a number of different types of fasting out there, and each individual athlete has different training schedules and energy needs. For example we have two methods of “time restricted eating”, one called “early TRF”, and one called “late TRF”. In early TRF we eat all of our calories earlier in the day, and fast through the evening and overnight. In the opposite- late TRF we fast overnight and into the mornings, eating all of our calories later in the day. This is a vastly different strategy than other forms of fasting which promote a smaller eating window (say, 4 hours), or entire days of no food intake. Comparing the outcomes of different studies (or even anecdotes online!) which utilize different fasting methods is truly comparing apples to oranges. 

Interestingly, sleep and exercise can also promote autophagy to some extent. Which begs the question; Is there any benefit to IF beyond what we might obtain as athletes who are already active and consistently getting adequate rest?

Some athletes have found that intermittent fasting seems to do wonders for their health and performance. When we take a closer look it may be that they’ve reduced their body fat percentage and with that improved their speed (which can be done but certainly isn’t a guarantee!) Or perhaps they now have better sleep quality from not eating a lot late in the evening. Some may even have fewer digestive complaints while on the track because they’re saving their large breakfast for after practice. Whatever the case if you’re unhappy with any aspect of your eating or performance there is definitely a benefit to taking a close look at the timing and composition of your meals to see if it jives with your training schedule, but picking an IF strategy that isn’t based on your personal needs is unlikely to pay off.

The bottom line

So, could intermittent fasting unlock your athletic performance potential? At this point, it doesn’t look particularly promising if it requires a disconnect between meal timing and training. While it may be worthwhile fat loss strategy to help some athletes continue to adequately fuel around their training schedule, there are far better performance enhancing strategies out there for most of us, like getting enough calories in to support training, and prioritizing rest and recovery. As an athlete if you’re trying to train while under-fueled, aren’t hitting your protein target for recovery, or are skipping out on sleep due to the timing of your eating window, IF is actually likely to impair performance, not enhance it.

On the flip side if your goal is a reduction in body fat, but you still want to train and perform your best, timing your calorie intake around the time you’re most active is actually a logical strategy. Fueling up before exercise, having a solid post-recovery meal, then limiting calories for the remainder of the day might be a better idea than trying to achieve the same result with an overall huge calorie deficit. The important thing to remember though, is that the fasting itself isn’t what’s enhancing performance, rather it’s the side effects of choosing it as your strategy.

Whatever you choose, be sure you’re still achieving your calorie goal (whether that’s maintaining weight or a small deficit for fat loss), get enough protein, and time your meals around your training schedule, not the opposite.  If you’re not able to eat enough in your feeding window to meet your nutrient targets, or aren’t seeing any performance benefit from a trial of IF, then it just isn’t for you. Remember, all of us do intermittent fasting to some extent overnight while we sleep anyway, so if you’re getting in a solid 8 hours of rest each night, you’re probably doing just fine regardless!


About the Author: Stephanie Hnatiuk is a Registered Dietitian and Personal Trainer who specializes in helping athletes reach their peak potential with nutrition.

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