Carbs Stay King
A runner's diet has always been one of regular and plentiful carbohydrates. Is this about to change with the likes of 'high protein low carb' or 'high fat low carb' diets?
Something new, different, and better is always going to make a headline somewhere on your phone, but when it comes to the idea of low-carb diets for runners the 'better' of the headline should be closely examined.
Though there are some scattered studies that suggest these alternate diets can produce similar and perhaps slightly better results, for marathoners, the details of those studies matter. The most commonly referenced of these studies show results from a 1 mile time trial or ultra-marathoners doing 100 mile races, both of which have drastically different energy demands than competitive marathoners. The reality is zero of the Olympic marathoners in Paris are on or were ever on a low carb diet during training.
If we are aiming to improve our marathon time, carbohydrates are and will always be the most important substrate to provide energy to our hungry muscles. If you are considering challenging this through a new diet all in an attempt to get faster, perhaps there is something more traditional that would be more effective, like more volume, more marathon-specific speed, or better quality and more abundant carbs. No big headlines there, just the basics, of which are often not fully utilized.