Hey, what's up, everyone? Welcome to another video. My name is Dylan, and I'm a psych and coach at CTS. And today we're going to be talking about fasted training. The theory goes that if you train in a fasted state, your body will be able to better utilize fat as a fuel source instead of carbohydrates, thereby leading to better endurance performance. But does this theory actually hold up to the science? I'll also touch on another potential method of doing this, which involves manipulating your diet to be higher in fat. And I'll talk about training your gut to handle higher carbohydrate loads, and how that fits into this whole fasted training conversation. At the end of the video, I'll talk about who should and should not be fasted training, as well as how to do it correctly. If you're new to this channel, I make weekly science-based training, racing, and gear related videos. If you want to learn how to get faster or just more about the science of training in general, then be sure to subscribe. And if you have a training question or a topic you'd like to see me cover in a future video, be sure to leave it down in the comments section below. I do my best to get to all the questions in the comments. Let's get this out of the way right off the bat. Carbohydrates are your fuel source for endurance exercise, and consuming carbs before, during, and after exercise improves your performance. Looking to this 2011 meta-analysis that looked at 88 randomized crossover studies on carbohydrate consumption and endurance performance, the conclusion is that carbohydrates show a large benefit to performance. I don't want to take up too much of this video talking about the importance of carbs, but I've already made quite a few videos on this subject and I'll leave them linked in the description below if you want to check them out. So if carbohydrates increase performance, why would anyone choose to train in a low carbohydrate state, either by following a low carb diet or fasting before training? The theory goes that if you train in a low carbohydrate state, you train your body to utilize fat as a fuel source, thereby preserving your carbohydrate stores and increasing your endurance performance. And there might be something to this. One of the physiological effects of training is reduced reliance on carbohydrates and pros appear to have an increased reliance on fat metabolism, even at higher power outputs. On top of that, if you're using less of your carbohydrate stores on a long ride, then presumably your chance of bonking would be lower. Let's first tackle trying to achieve a lower reliance on carbohydrates by following a high fat diet.  Perhaps consuming a low carb diet regularly during training and then loading up on carbs on race day would give you the best of both worlds. This study tested just that by having subjects consume a normal carb rich diet or a high fat diet for six days followed by one day of carb loading.  However, although there was no difference in 100k time trial performance, times were three minutes and 44 seconds slower when subjects were fed the high fat diet. Subjects also performed significantly worse in one kilometer sprints after eating the high fat diet. That's right, a high fat diet with carbohydrate loading performed worse in a test of endurance like a 100 kilometer ride and not simply a 20 minute test for example where you might expect carbohydrates to reign supreme. And this isn't an isolated study coming to this conclusion. This review on carbohydrate dependence in endurance athletes concluded that despite renewed popular interest in high fat, low carb diets for endurance sports, fat rich diets do not spare carbohydrates or improve training capacity and performance, but instead directly impair rates of muscle glycogenolysis and energy flux. And to really drive this point home for all you keto people who are drinking butter in your coffee and avoiding the fruit aisle at the grocery store like it's the plague. From this review on periodized nutrition for athletes, the ketogenic diet has received considerable attention in the popular press and many claims have been made recently. However, it is important to realize that to date, not a single study has demonstrated performance benefits of a ketogenic diet. Yeah, but Dylan, I heard from this guy on the Fat Panatic podcast that large fried butter sticks dipped in coconut oil and then wrapped in bacon is the perfect pre-ride food. And this guy is like totally jacked too. So I just think your science is a little flawed. It appears that chronically withholding carbohydrates may actually be detrimental to your ability to oxidize them, which we certainly do not want because you want to be consuming a lot of carbohydrates on race day to maximize performance. The potential solution here is to train in a fasted state. For example, if you ride in the morning without eating breakfast, then your glycogen levels will already be depleted from a night of fasting and you could potentially get those metabolic benefits without having to do a high fat diet. Great idea in theory, but does it actually work? This study on endurance training in a fasted state had subjects complete a six week training program where they completed workouts in either a fasted or a fed state. The results, while the fasted group saw a lower drop in blood glucose indicating that they were using more fat as fuel, this didn't translate into a performance benefit in a 60 minute time trial over the control group. And many studies on fasted training see similar results. This review came to the conclusion that despite increasing the muscle adaptive response and reducing the reliance on carbohydrate utilization during exercise, there is no clear evidence that these strategies enhance exercise performance. Increasing fat utilization is fine, I guess, but if it's not leading to an increase in performance, then what's the point? And on top of this carbohydrates increase performance, so training in a fasted state may lead to lower quality workouts. This brings to light one very important flaw with these studies, and that's that the fasted group performs every workout fasted. I don't know about you, but heading out for a high-intensity VO2 max interval session with an empty stomach sounds like a recipe for ending up in a ditch fully bonked, begging for a ride back to town, or at the very least a gel. Hmm, yeah, sounds like how I finish every ride. However, what if you did your high-intensity sessions fed and your low-intensity sessions fasted? Could this be the best of both worlds? This study on the periodization of carbohydrates put this to the test by having the experimental group perform workouts in an order where they would do a high-intensity glycogen-depleting workout in a fed state, and then do a low-intensity workout the next day after an overnight fast. What they found was that the fasted group significantly improved their 20k time trial performance, while the control group did not.  Now, it seems like we're getting somewhere. However, it's important to note that these are the only two studies investigating this style of fasted training, so the results should be taken with a grain of salt. That being said, it does make sense that fasted training may only work if done strategically. You want to be well-fed for your high-intensity session so that the quality is high, and there may be another important reason why you don't want to do every workout fasted. From this review article on carbohydrate availability, athletes should practice trained low workouts in conjunction with sessions undertaken with normal or high carbohydrate availability so that their capacity to oxidize carbohydrates isn't blunted on race day. This brings us to the next point and something that I alluded to at the beginning of the video. You do not want to compromise your body's ability to utilize carbohydrates, and there has been research into training the gut to better handle carbohydrates and has shown favorable results. Going back to the review on periodized nutrition for athletes, a high carbohydrate diet will increase the number of sodium glucose transporters in the intestine as well as the activity of the transporters, allowing greater carbohydrate absorption and oxidation during exercise. This may reduce the chances of developing GI issues. They conclude that nutritional training can improve gastric emptying and absorption, and likely reduce chances or severity of GI problems thereby improving endurance performance. If you constantly train in a fasted state, just like with consuming a low carb diet, your body won't be able to use carbohydrates as efficiently during exercise. But how exactly does one go about training the gut? Ooh, let me guess.  Well, to start your day-to-day diet should be filled with healthy whole food carbohydrates like fruits, vegetables, legumes, etc. Well, I must say that is very disappointing. Fruits are great to consume in your daily diet as fructose consumption has been shown to accelerate gastric emptying of fructose, which is an important fuel source if you want to maximize carbohydrate absorption per hour. It's also important to train your gut on the bike, and high-intensity days are a great time to do this because you want to be well fed for these workouts anyway. Use these days to test out your race nutrition strategy. A good place to start is trying to consume 60 grams of carbohydrates per hour. If you combine carbohydrate sources, then you could work your way up to 90 grams of carbs per hour. The limit of absorption of glucose alone is around 1 gram per minute or 60 grams per hour, but combining different carbohydrate sources such as glucose and fructose have been shown to increase carbohydrate oxidation rates by 20 to 50 percent because fructose can utilize a different transport pathway. This review confirmed these findings stating that a 2 to 1 multidextrin to fructose ratio appears to be optimal and benefits endurance performance. However, consuming this many carbs per hour takes training, so be sure you work your way up to 90 grams per hour before you attempt it in a race. One of my very early videos on this channel was about fasted training, and I came to the conclusion that if you can do fasted training then it may be worth giving it a try, but if you're like me and you wake up every morning starving and can't function until you get some breakfast inside of you, then it's probably not a big deal if you skip out on fasted training. I've since done some rethinking on this though. I've been doing fasted runs first thing in the morning throughout the off season, and to be honest, it isn't that bad. Given that I'm an alternate endurance athlete who does events that last all day, carbohydrate preservation is very important to me, so I plan on giving fasted training another shot this year. Just like with anything, it does appear to be something that you can get used to. However, I don't think that everyone needs to be doing fasted training. For example, if your races are relatively short, say you're a cross country mountain bike racer, or a crit racer, or you do cyclocross, then running out of carbs during those races isn't usually the limiting factor. However, the longer your races get, the more important carbohydrate preservation becomes, and the more potential benefits you'll see from fasted training. If you're an alternate endurance athlete, it may be worth considering doing some fasted rides. One important thing to note is that men may respond better to fasted training than women. Women already naturally utilize a higher proportion of fat, which may be part of the reason why. If you do decide to try fasted training, make sure that you do it on low-intensity days. Your high-intensity workouts need to be done in a well-fed state, because you want to maximize the quality of those workouts, and practicing consuming a lot of carbohydrates during those workouts will be beneficial for your gut come race day. And finally, whatever you do, don't fall for the bro science and follow a low carb or ketogenic diet. That's it there, I'm out. Thanks for watching. I hope you guys found this information helpful. If you liked this video, be sure to give it a like, share it with a friend, and subscribe. And if you want to be notified every time I put out a video, be sure to hit the notification bell as well. If you're looking for a coach, if you sign up for CTS, be sure to use my code, CTSDJ, to save $40 by waiving the registration fee. Details are down in the description.