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.

Carbs With Your Paleolithic Diet?

Picture by Lord Jim from Flickr

I've previously written on the Paleolithic or caveman diet before, which typically consists of hunted meats and fish and food that can be gathered like eggs, insects, fruits, seeds plants and herbs etc.

As a result you're supposed to get healthier, low fat protein, healthier fats and much less dairy and grain (or carbohydrates) than what we normally eat today.

A recent published article however suggests that the Paleo diet did in fact consist of lots of starchy carbohydrates.

The researchers put together information from genetics, archaeology, physiology and nutrition to come up with a theory that our Paleolithic ancestors did actually eat starchy plants like potatoes and possibly even cooking them over fires.

They also suggested that eating carbs help made our brains larger. Without carbs, we may be very different today. We may also not be runners like we can be now.

The authors wrote that carbohydrates are essential for long distance running which is how our ancestors chased down and captured prey. We get energy from glycogen stored n our bodies during vigorous exercise. Our glycogen stores normally lasts about 20 miles (or 32 km) and if you don't eat or drink, you'll hit the wall.

Even evolutionary biologist Daniel Liberman, who has written so much about humans and barefoot running said "The idea that people shouldn't eat carbohydrates is just silly, we've been eating carbohydrates for a long time."

Lieberman however isn't convinced that carbs helped Paleo hunters run better. His research suggested that Paleo hunters who chased down their prey didn't have to run that fast as they actually walked and ran. At those speeds (to keep up with a wounded prey usually) they may not need a lot of carbohydrates. Their bodies probably used more fat instead.

I've written before that relying on fat may help running performance. This is especially true if you have trained your body to use fat as fuel (which our bodies have plenty). It allows us to run further without hitting the wall.

Some have proposed that this may be better for ultra marathon distances (since you tend to run slower). However as speed increases, carbohydrates tend to be vital, especially if you want to run long and fast, suggested Lieberman.

Do take note that the carbs our Paleo ancestors ate were complex carbohydrates and not the overly processed and refined carbohydrates we get on supermarket shelves today.

The authors suggested that we need to be careful when trying to replicate ancestral diets as we still do not know exactly what Paleo man ate.

Looks like you can and should eat complex carbs, especially if you wanna race long and fast.

Reference

Hardy K, Brand-Miller J et al (2015). The Importance Of Dietary Carbohydrate In Human Evolution. The Quarterly Review Of Biology. 90(3): 251-268. DOI. 10.1086/682587.

Cavemen and dinosaurs? by Orln Zebest from Flickr

Is Carbohydrate Loading Still Relevant For Endurance Sports?

Picture by Weena from Flickr

Runners accept that carbo loading to be a norm prior to a race. Exercise physiologists have long told us that our muscles primarily use muscle glycogen (what the carbohydrate we eat turns into) during high intensity exercise. Hence we are advised to eat large amounts of carbohydrate before and during exercise.

However, 3 famous exercise scientists have come forward and suggested this is not totally logical. Since most if not all elite (and recreational) athletes spend most of their time training at submaximal levels (and not at high intensities) is it necessary to always eat a high carbohydrate diet?

The authors suggest that there is a lack of evidence surrounding low carb diets and its relationship to performance in the endurance exercise. Out of only 11 published studies done previously, 9 of them actually suggests that the subjects perform better or at least the same on a low carb diet compared to a high carb diet.

As a matter of fact only one study out of the 11 used subjects that were used to a low carb diet. Why is this important? Well just like a runner who have just changed shoes from a "regular cushioned" pair to a thinner soled pair will need time to adapt, a low carb eater will need time to adapt if he/ she has been used to a typical high carb diet (used by most runners).

As humans store limited amounts muscle glycogen in the body, this glycogen is mostly depleted after 20 miles of running. Hence runners often "hit the wall" after 20 miles into the marathon. Our bodies however store large amounts of fat in the body, if we can utilize the fat stores we have, we would be able to run two marathons back to back.

One of the authors (Phinney) in the current paper published a previous study in which cyclists after being on a low carb diet for three weeks used significantly more fat than they had on a typical high carb diet. Moreover, they also showed a four fold reduction in the use of muscle glycogen. This is remarkable as it was thought to very difficult (or even impossible) to produce energy purely from utilizing body fat (and not using muscle glycogen) at such high intensities of exercise.

Based on the Paleo outlook, the authors suggested that the subjects were able to have instant access to their fat reserves at all times since they live and train on low blood sugar levels (based on their low carb diet). This metabolism is similar to our ancestors in the prehistoric (or caveman era) where they were predatory hunters.

Since there is much variation among athletes, there are many unanswered questions regarding low carb diets especially since there are so many more studies done on high carb diets.

We await more research on the effectiveness on low carb diets since there may be long term health consequences of regularly eating a high carbohydrate diet since there are increasing numbers of recreational athletes who are insulin resistant (IR 4-6) and those eating too much refined sugar from high carbohydrate diets may be at risk of developing Type II Diabetes Mellitus.

Reference

Nokes T, Volek JS and Phinney SD. (2014). Low-carbohydrate Diets For Athletes: What Evidence? BJSM. doi: 10. 1136/bjsports-2014-093824.

Phinney SD et al (1983). The Human Metabolic Response To Chronic Ketosis Without Caloric Restriction: Preservation Of Submaximal exercise Capability With Reduced Carbohydrate Oxidation. Metabolism. Aug 32(8): 768-776.

Low carb diet

Picture from Flickr