Keto, ketosis, ketones, net carbs... These words are taking over social media rapidly and everyone knows at least one person who is now “keto”. What does that actually mean? What is the benefit of following a ketogenic diet in regards to athletic performance? What are the potential downfalls?
Disclaimer: We are ALL unique and what works well for some people will not work for others. We’re not interested in case studies where so and so felt great on terrible on a certain diet. We really don’t mind if you love this diet, hate it or fall somewhere in between. What we’re doing is looking for the path forward thats going to help the most people while giving them the best chance of success. As so many people are interested in keto these days, we wanted to summarize the “big picture” aspects of the keto world as it relates to performance, weight loss and overall chance of success. We are NOT focusing on epilepsy or neurological conditions, where there’s been benefits shown as early as the 1930’s.
Before we get too far…
To start, we want to highlight a few key facts about nutrition to be mindful of while examining any diet. First, the value of protein. This is probably the least sexy macro that everyone probably understands they need, but often have trouble achieving proper intake. Bros think they need too much and women tend to under-consume. Second, carbohydrates. These bad boys are the fuel behind your fire, the vessel that delivers your fiber, and the micronutrient powerhouses. Last but not least, fat. Fat is hormone regulating, helps us absorb vitamins, and provides energy for our bodies at rest and under certain specific exercise time domains (Read: LONG efforts). All three are vital and important for their unique roles.
So, what is keto?
Keto is a very low carb, high fat, moderate protein diet. It aims to be so low carb that the body begins producing ketones in the liver for energy. To reach a state of ketosis (where the body is producing these ketones) the dieter attempts to eat 20 net carbs or less a day. If counting macros, this usually looks like 5% of calories coming from carbs. Net carbs are determined by taking the amount of carbohydrates in grams minus the grams of fiber. The idea comes from the fact our bodies cannot breakdown fiber therefore the body is not truly utilizing it in the means of energy. This is not to say that fiber is not extremely crucial to a healthy diet (it is, but that’s a topic for another day).
The idea of consuming a high fat diet has been around for centuries, the Inuit people are a great example and are notoriously known for their high fat low carb diet majorly consisting of whale blubber. The Kitavan population is the opposite end of the spectrum, consuming a diet primarily of carbohydrates. Both populations have minimal disease, no problem with obesity, and/or longevity. How is this possible? Before farming came into play, cultures consumed foods dependent on their regions and availability not based on knowledge of nutrition or perception of health benefits. Being able to feed the masses on farmed products was wildly more efficient than hunting and quickly shifted the emphasis on meat to grains and vegetables. We now live in a world where we have access to anything we could ever want to consume. As athletes, this raises the question of how to fuel for superior performance.
Curiosity as to whether one macro was more vital or useful in health and performance than another sparked a plethora of studies and research. Traditionally, carbohydrates have been the renowned champion of performance, particularly in anaerobic exercise modalities such as sprinting, lifting, or other high intensity sports. Some studies have found functionality in a high fat diet under submaximal aerobic conditions when properly supplemented.
Let’s look at some studies…
Two studies completed in the 1980s, one at the University of Vermont and one at MIT, looked at the performance of individuals on a treadmill and stationary ergometer, respectively, from their baseline level of VO2 max and performance on a normal carbohydrate diet to that on a ketogenic diet. The Vermont study restricted calories as well as carbohydrates and did not allow dieters to workout outside of the testing situations. Their VO2 did not change but their endurance did increase over the six week period. The first week following a ketogenic low calorie diet, however, they did notice a reduction in performance throughout all participants. The participants lost weight and were not previously active or conditioned so it is hard to tell if their increased work capacity was due to less required energy expenditure due to loss of size, increased exposure to aerobic work, or the nutrition in itself. The second study combated these questions by using competitive cyclists and fed them to maintain weight. Again, in the first week the participants saw a decline in performance, but after four weeks of the ketogenic diet there was no real change to their performance. It is important to note that both studies supplemented sodium and potassium and that the analysis of the two studies concluded that while the results show no short-term disadvantage to a ketogenic diet on aerobic performance, it would not recommend a ketogenic diet to persons partaking in anaerobic activities such as sprinting or weightlifting.
Earlier than that, in 1939, two Danish scientists tested participants endurance on a stationary bicycle for three weeks, each week moving from low carb, moderate carb, then to high carb diets. When subjects were given the high carb diet their performance increased 2.5 times what it was for the low carb week.
During the second world war, Kart experimented by giving soldiers pemmican, a mixture of dried meat and fat, to test its functionality as a lightweight food ration. The study lasted three days as the soldiers could not perform their tasks which included pulling heavy sleds through snow.
A 2016 study looked at changes in performance due to the diets of elite race walkers. Some were given a low carb high fat diet, others a periodised carb diet, and the rest a high carb diet. They provided all meals, drinks, and snacks for the athletes to ensure the study was extremely controlled. They found, as expected, the LCHF diet produced the highest levels of fat oxidation in exercise. Fat oxidation is where the body is burning fat as fuel. They ALSO found that the fat oxidation produced a higher need of oxygen consumption, meaning the LCHF group had to work harder to produce the same level of energy as the periodised and high carb groups. With that, the periodised and high carb group both found improvement in their 10km race whereas the LCHF group did not. The study goes on to analyze that the ATP (energy molecule) production from carbohydrates was greater than that of fat. It continues to infer that if an athlete is working well under their lactate threshold, it is possible to compensate for the difference in energy production by increasing oxygen intake, but once the intensity of work has increased to higher levels, the athlete will be limited greatly in capacity and performance.
In 1996, another study showed significantly decreased respiratory exchange ratios in the LCHF group than the high carb group. Heart rates were also noticeably higher in the high fat group. The study concluded that low carbohydrate high fat diets are detrimental to improvement in endurance performance.
Looking to determine which popular diet was superior, low carb or low fat, Stanford University, coupled with the National Institute of Health, the Nutrition Science Initiative, and a group of nutrition experts followed the lives of over 600 people for a year. Participants were either prescribed to the low carb or low fat diet and encouraged to eat whole, nutrient dense, unprocessed foods along with their specific carb or fat limitations. By the third month both groups were struggling to hit the targets of 20 grams of fat or carbs and were consuming an extra 20 grams of fat (198 cals) and almost 100 grams of carbs (400 cals) in their subsequent groupings. This is well over the prescribed carb limit for the keto diet. In addition to not truly maintaining a “low carb” diet, the study had a 21% drop out rate and no real difference in weight loss between the two groups. This suggested to researchers that either diet has cause to be effective so long as there is the critical element of sustainability for each individual.
Can the body use fat as the (nearly) sole fuel source? Sure. Is fat as fuel as effective or efficient as carbohydrates in regards to performance? No.
Can the body sustain fat as its primary fuel source healthily for a lifetime? Unclear, but we predict that its not likely. The initial weight loss claims from keto believers is primarily water weight. When carbs are cut and the body uses up its stored glycogen, it sheds the water associated with the stores. For every one gram of glycogen (carbohydrate) stored in the body, there are roughly three grams of water stored. This is not lasting weight loss as the water will be retained once again as carbs are reintroduced.
To summarize…
As a company formed to support athletes and their performance via nutrition and lifestyle, M2 continues to support higher carb diets for athletes. We want your PRs to continuously increase, your endurance to last for days, and your recovery to be prompt and complete. Every macronutrient has an important role, and should be utilized in amounts that offer optimization of their attributes. We are NOT saying that the general public shouldn’t eat less processed carbs… they probably should just stop eating so much crap all together. We don’t want our athletes to just be able to function with their nutrition, we want them to thrive.