Fuelling for the Long Haul

Is carb loading necessary. We get asked this question a lot.  Recently I read the story of Portuguese ultra-marathoner Ana Teixeira whose diet consists of only meat. A few week Greg’s cousin, an avid runner, posted her pre-race dinner on Instragram. It was a heaping plate of ravioli. Talk about extremes!

Carb loading has been around for so long that we no longer question its efficacy. Athletes of all ability, trainers and nutritionists simply assume that it must be the right way to fuel endurance sports.  Perhaps not. At least not as we’ve carb loaded in the past.

The whole foundation of carb loading rests on the fact that carbohydrates are the easiest and most accessible form of fuel. Our bodies store carbohydrates in the muscles and liver in the form of glycogen. This stored energy can be quickly broken down to fuel muscles during high intensity exercise.

The amount of additional carbohydrates that can be stored is largely individual and based on fitness level and current diet. An untrained person consuming a high carbohydrate (75% of total calories) diet may have total stores of 490g. A highly trained athlete consuming a moderate carbohydrate diet (45% of calories) will have 330g of stored glycogen. If this same athlete consumed a diet of 75% carbohydrates his potential glycogen stores could reach 880g.

Having this extra on-board energy sounds like a great idea.  Carbohydrate storage comes with additional weight in the form of water. A runner could find himself six to eight pounds heavier on race day. That extra weight may impact running economy.  Despite the extra energy stored in the muscles and liver, current research suggests only a 2 to 3 percent increase in endurance performance.  Furthermore, our bodies only store about two hours’ worth of carbohydrates.

At the Other End of the Spectrum

At the opposite end of the carb spectrum, studies involving athletes and low carb diets have gotten mixed results. Some find no difference in performance between high carb and low carb dieters while others find that low carb diets benefit endurance athletes.  Low carb diets help preserve glycogen stores and may help athletes avoid the dreaded “bonk.” Given that the body can only store a couple of hours’ worth of carbohydrate energy and the average runner finishes a marathon in over four hours, this is a tremendous benefit. Also our bodies’ stores of fat are much greater, therefore making it a better source of energy. There are 9 calories for each gram of fat compared to 4 calories for each gram of carbohydrate.

Carb loading in the past meant several days of low carb dieting combined with intense exercise followed by several rest days and high carb refeeding. Mainstream carb loading is all about the pasta dinner the night before the big event.  Some studies suggest that training in a low carb state and then replenishing carbohydrate stores in the days leading up to the event may be the best way to fuel performance.

We fuel our adventure races with a high fat, low carb breakfast.

We fuel our adventure races with a high fat, low carb breakfast.

There is no way I could eat a plate of pasta and run the next morning. Well I’d be running alright…to the port-a-potty. I’ve been eating a mostly paleo diet for about five years and have noticed a significant difference in my endurance. My favourite pre-race meal is 2 to 3 pieces of bacon, 3 eggs, tomato and avocado.  I have energy for hours and don’t have to rely on gels or sports drinks.  Sports nutrition is highly individualized. It takes several months of experimenting to find the right combination of fat, protein and carbohydrate that fuels performance.

How do you fuel your fitness?

By Nyree Segui RHN