Can Ketogenic/LCHF Diets Make You a Better Athlete?
Many dietitians had hoped that the keto/LCHF trend would die with Dr. Atkins back in 2003, but the low-carb movement is still going strong. Nowadays, it’s not just for people trying to manage their weight or symptoms of epilepsy; a few professional athletes have reportedly jumped on the bandwagon, in hopes of giving an edge to their performance.
Keto What? LCHF Who?
Normally, our bodies rely on carbohydrates for energy. When food is scarce and the carbohydrate (glycogen) stores in our muscles and liver run out, our bodies enter a state of ketosis, and draws from our fat stores to create compounds called ketones for energy instead.
The ketogenic diet was first invented in the 1920’s as a treatment for epilepsy – researchers found that the frequency of epileptic seizures decreased in some patients who were fasting, and noticed that these patients had higher levels of ketones in their blood. They later discovered that they could “trick” the body to go into ketosis without fasting by feeding it a diet that was extremely low-carb, high-fat (LCHF). The diet only allows about 10-20 g carbohydrate per day, or less than the amount of carbs in an apple. About 60-80% of the calories of a ketogenic diet come from fat, more than double what is recommended in general healthy eating guidelines.
More recently, the Atkins diet popularized the ketogenic diet as one for weight loss, based on the idea that if your body is burning fat for energy, then it must lose more fat. Ketogenic/LCHF diets generally result in more weight loss initially, partly due to the loss of water weight as the glycogen stores in our muscles are depleted. In the long-term, however, it’s still calories that dictate weight loss.
It should be noted that there are some LCHF diets that do not achieve ketosis; while they do recommend restricting carbs and/or increasing fat intake compared to standard Western diets, it is not to the point where the body produces ketones. One example might be the Paleo diet – though it’s not technically a LCHF diet, the restriction of grains, legumes and dairy means that many people end up eating less carbohydrates than they normally would (though you could still get lots from fruit and starchy root vegetables). Interestingly, some proponents of the Paleo diet, like The Paleo Solution author Robb Wolf, do advocate being in ketosis as part of the Paleo lifestyle. (I mean, it does kinda make sense, because cavemen were starving all the time, right?)
Why Keto for Sport?
While our bodies prefer carbohydrates as a source of energy, in some ways it’s not very efficient – our glycogen stores can only last us up to about two hours of continuous activity, forcing endurance athletes like marathoners and cyclists to have to eat during competition. In comparison, even the leanest people have enough energy in their fat stores to last them for much longer, so it’s thought that switching to a ketogenic diet can help athletes tap into that source.
Another reason that came up in my research was that it could be a safer alternative to some of the extreme weight cutting practices that happen in weight class sports. This doesn’t make a lot of sense to me because in the two studies I read (here and here – trigger warning: weight loss specifics) The amount of weight loss achieved was less than what I have seen some of my teammates in Muay Thai lose (mainly via dehydration) for their competitions.
Ketogenic/LCHF Diets and Endurance Athletes
So, is there an advantage to burning fat instead of carbs in endurance sports? The short answer is, not really. First off, it takes time for the body to adapt to a ketogenic diet – studies consistently show that it takes at least a week on the ketogenic diet for the body to start using fat as an energy source in a way that makes up for what would normally come from carbohydrates. Studies on LCHF diets without ketosis show a slightly shorter adaptation time.
Still, once these adapted subjects are put to the test, the best we can say is that performance is comparable to people following a regular diet – most studies show no significant differences in maximum workload (usually measured as VO2max, or maximal oxygen uptake), endurance (usually measured as time to exhaustion) or speed (usually measured as time trials). While some studies show some advantages in moderate intensity activity, keto/LCHF diets really fall down when it comes to higher intensity exercise. At a molecular level, our body is simply faster at generating energy from carbohydrates than it does from fat, and during high intensity exercise, the body just can’t tap into energy from fat quick enough to meet the higher energy needs.
While endurance events are generally considered steady, moderate intensity activity (I know most of us are reading this thinking, “Ha!”) Key parts of the race that require higher energy output – hill climbs, sprints, breakaways – can determine the outcome.
To make up for this, one strategy that is being studied is the “carb up”. First, subjects are put on a LCHF diet to adapt to using more fat for energy, then 1-3 days before competition, they are switched to a high-carb diet so that the body has carbohydrates to draw from during the high intensity parts of the activity.
It sounds good on paper, but so far, the results are not promising. Though some studies showed slight, often non-significant improvements in performance (4-8%) in time trials overall (enough to win a race?), there were no improvements in higher-intensity activity.
What gives? It turns out that at a molecular level, while LCHF diets make our bodies more efficient at using fat, at the same time, they makes us less efficient at using carbs, so even when more carbs become available, the body cannot take advantage of it.
“#Keto & #LCHF diets may help for mod intensity #exercise; not effective for high intensity.”
Ketogenic/LCHF Diets and Strength & Power Athletes
Most of the interest in keto/LCHF diets and sports performance have to do with endurance sports, though there have been a few studies looking at these diets in strength/power sports, usually in the context of athletes choosing these diets to help make weight.
As mentioned earlier, I unfortunately don’t think people are going to give up their extreme weight cut practices in favour of a keto diet from a numbers standpoint. Even from a body composition standpoint, things don’t look really good. Only one of two studies showed a significant loss in fat mass compared to the standard diet group; both studies showed that both the ketogenic diet and control groups maintained their lean body mass during the length of the study (3-4 weeks) Both studies also showed no significant improvements in strength after the ketogenic diet, and when compared to the control group.
If bulking up is your goal, forget about it! It is generally agreed that ketogenic and LCHF diets lead to changes in our body that block the biochemical and molecular pathways that would normally lead to muscle growth.
“Don’t even bother with #keto and #LCHF diets if you do strength/power sports.”
A Word of Caution
Conducting sports nutrition research is hard. It’s difficult to find trained athletes to do the research, so most studies only have a handful of subjects – in the studies that I looked at, the largest study had 20 people (though only 10 people were in the ketogenic diet group), with most studies having somewhere between 5-8 subjects. Also, the studies aren’t very long – most last 1-2 weeks, so it’s hard to say what the effects of following the LCHF diet for several months, let alone a year, would have on performance. Finally, because trained athletes are used in the research, it’s also difficult to see how this may relate to the average Joe or Jane who “only” works out for an hour or two, a few days a week.
In addition, it seems that what exactly constitutes a keto, LCHF or even a standard diet is a moving target. While the original ketogenic diet was 80% fat, 15% protein and 5% carbohydrate, two of the studies I looked at gave participants a diet that was 55% fat, 41% protein and 5% carbohydrate, while another gave a ratio of 70/15/15. The definition of LCHF is even more broad, including any diet that is > 60% fat and < 25% carbohydrates. To further complicate matters, in many of these studies, the diet is not controlled, and study subjects are simply given instruction on what to eat, with their only accountability being a 3-day food record.
In Summary
While in the past it was thought that all athletes needed higher carbohydrate diets to fuel their activity, current guidelines now suggest that carb intake needs to be adjusted according to an athlete’s training goals and schedule. Ketogenic and LCHF diets can lead to adaptations at the cellular level, but so far that has not translated to performance outcomes. Still, with so many limitations when it comes to sports nutrition research, we are really left with more questions than answers.
As with anything related to diet and nutrition, a lot of it is based on emotional rhetoric and “this is what worked for me” as opposed to actual scientific evidence. With low-carb being so popular in the weight loss world, it only makes sense that you have similarly passionate people in the world of sport. In a recent review of the research on LCHF diets and sports performance, Louise Burke, sports dietitian and head of sports nutrition at the Australian Sports Commission, wrote:
“Peer-reviewed publications from the key scientific protagonists of the LCHF movement [ed note: the paper goes on to cite three studies by Tim Noakes, Jeff Volek and Stephen Phinney] generally show measured and thoughtful insights […] Discussion generally targets the potential for ‘some’ athletes to respond to this different dietary approach […]
The apparent caution expressed in peer-reviewed publications is generally not present in other outputs from the same authors. Laybooks, web-based information, and social media enthusiastically promote the LCHF dietary approach for a larger group of athletes or athletes in general, with a positive view that this is an evidence-based strategy.”
“The current literature on LCHF is relentless in promoting misunderstanding or misinformation on the current guidelines for athletes in relation to carbohydrate intake in the training or competition diet […] As a contributor to the evolution of the current sports nutrition guidelines, which have moved away from a universal approach to any aspect of the athlete’s diet, […] this author finds such misrepresentation to be a disappointing thread.”
