The world is abuzz with Lebron James' recent decision to undertake a low carbohydrate Paleo diet and the more svelte physique that followed. While the aesthetic change to his decision is readily apparent, the performance ramifications wait to be seen. As someone who has used principles of the Paleo diet for my own personal nutrition as well as those of my clients for the past 5 years, I am familiar with the ins and outs of this type of nutrition program. While paying more attention to the quality of one's diet can improve performance, cutting carbohydrates is not always the best idea for someone in a sport like basketball.
The type of fuel a person uses is dependent on the type of activity they partake in. Someone who sits at a desk and does low level physical activity throughout the day doesn't need a large amount of carbohydrate because this type of activity predominantly uses fat. If this person were to get up and sprint on and off for 30 seconds at a time they would shift to burning glucose, which is what the body turns carbohydrates in to. In the event this person decides not to eat carbohydrate and still tries to perform physical activity that requires glucose from carbohydrates, they will eventually "bonk". This means they will not be able to produce energy fast enough to keep up with demand. While they will be able to make glucose from non-carbohydrate energy sources, the body cannot produce it fast enough to keep up with the demands of a sport like basketball. My prediction: Either Lebron starts eating carbohydratess or his game will suffer.
So if slashing carbohydrates isn't going to give a performance advantage, how can following principles of the Paleo diet improve athletic performance? To better understand how this works, it's important to get a basic understanding of how the immune system works. I promise this won't get too technical. Monocytes are essentially immature white blood cells, they roam around the bloodstream like a couple of high schoolers looking for something to do. Just like a high schooler, they have no specialized skill because they haven't received instruction yet. When monocytes encounter an area of the body in need, they quickly receive a PhD in what needs to be done from the environment and differentiate in to a more specialized type of cell that can carry out a more specific task in that tissue. This could be to identify invaders, fight an infection, or repair damage from exercise. An important point to understand in this process is that it is often inflammation that gives the monocytes the instructions and, thus their PhD in what to do. Once a monocyte has been given instructions on what to do by a certain tissue, they are essentially useless to any other tissue in the body.
Neutrophils are another type of white blood cell, the most numerous. Neutrophils act and move quickly to sites of inflammation to help battle invaders by engulfing them, secreting antimicrobial proteins that help digest invaders, and increasing inflammation to signal there is an infection. The function of monocytes and neutrophils is important to understanding how the principles of the Paleo diet can improve athletic performance.
The Paleo diet avoids refined sugars/processed foods, grains, legumes and dairy and replaces them with fruit and vegetables. Many people elect to eat large quantities of meat as well, but since most people eat large quantities of meat regardless of whether they eat a Paleo diet or not, we'll skim past that part(FYI, I recommend a moderate level of meat consumptions). The gluten in grains and casein in dairy are two proteins that can increase inflammation in the GI tract. An inflamed GI tract could hijack monocytes that would be better served helping you recover from exercise induced damage to muscle tissue.
In addition to tying up monocytes that could help recovery, GI inflammation also increases intestinal permeability to lipopolysaccharide(LPS). LPS drives the immune system nuts and induces insulin resistance in muscle and fat tissue to preserve glucose for the immune system. Since insulin sensitivity is the primary dictator of an athletes ability to replenish glycogen stores after training or competition, causing insulin resistance at any point in the recovery process can be bad for performance.
One final piece of the puzzle is how neutrophils respond to refined sugars. Ingestion of large amounts of refined sugars has been shown to reduce the ability of
neutrophils to engulf invaders for up to 5 hours post-ingestion while
starches had not effects(1). While this effect likely has a modest direct effect on exercise recovery, it will have a greater impact on susceptibility to infection which, over the long term, can negatively impact performance by taking an athlete away from training.
While many people attribute the benefits of a Paleo diet to a low carbohydrate content, most of the positive benefits of the diet occur because the quality of the diet changes. By improving the quality of your diet, you can improve athletic performance by improving recovery through better immune system function. Furthermore, if you participate in a sport that primarily relies on glucose for energy, cutting carbohydrates will have a deleterious effect on performance. My prediction for Lebron James is that he will either increase his carbohydrate intake during the season, or you will see at least a minor drop in his performance.