Carbohydrates Still The Best Energy Source For Racing

Picture by Erik Stattin from Flick.

Stick to your carbohydrate diet if you want to race well? Or train your body to burn more fat to be more effective in sustaining your effort. Much has been debated over how much carbohydrates and fat we need in our diet to enhance running (or endurance) performance.

Since our bodies can only hold limited amounts of muscle glycogen (or carbohydrates), we usually "hit the wall" after about 20 miles of running. Our bodies store large amounts of fat and if we can utilize the fat stores, we can potentially rely less on carbs.

And fat-adapted running diet is getting popular, especially in the long/ ultra distance running community in an attempt to teach their bodies to use fat (instead of carbs) for fuel.

Prominent exercise physiologist Tim Noakes has suggested that training your body to burn more fat is a more effective way to sustain effort (especially in a long race). Noakes may be right about utilizing fat for ultra distances and we await more research from him.

But carbs may be better if you are running high intensity intervals or racing hard and fast, so says a recently published research.

The researchers studied a group of male competitive runners in four randomized trials running on a treadmill at a speed of 95 per cent of their best half marathon time to exhaustion.

The runners consumed a pre run meal before each trial with different nutritional values. Runners in the first two trials were fed carbs in the form of a jelly. Runners in the next two trials fasted overnight and were given a jelly that looked and tasted the same to the carb group but contained no calories.

Runners in trials two and four were given nicotinic acid which prevented the use of fat stores during testing. This is to test whether blocking the use of fat as a fuel hampered run performance.

Results showed that majority of the time, (83-91 per cent) carbohydrates were the source of primary fuel. The nicotinic acid did not affect the runner's performance or the body's ability to use carbohydrates as fuel. The runners did use a small amount of fat as fuel, but the main source was still carbohydrates.

Your friends or other runners may want to experiment with utilizing more fat to fuel their runs, but this study shows that at least for races up to half marathon, carbohydrates are still best for getting you to the finish line or clocking your personal best timing.


Reference

Lackey JJ, Burke LM et al (2015). Altering Fatty Acid Availability Does Not Impair Prolonged, Continous Running to Fatigue: Evidence For Carbohydrate Dependence. J App Physiol. DOI:10.1152/japplphysiol.00855.2015.

**Note from a runner

A friend who's been on a low carb,  high fat Paleo diet shared that adding carbs back to his diet can be discouraging. For every ounce of carbohydrate he ate after training his body to be used to low carbs, his body stored three ounces of water. His weight shot up quickly.