January 28, 2011
This article is Part 1 of a two-part series from Ben Greenfield on the benefits of carbohydrate restriction during training. If you have questions or comments, please leave them below!
You roll out of bed and glance at your watch. You've got a 12 mile run on-tap for the day, and limited time to get it in. Do you lace up and head out without grabbing a banana, bagel or handful of sports gels, or do you make sure you have sugar to consume before and during the effort?
If you're a good little endurance athlete, you probably raised your hand and said “Eat!”.
But the entire basis for posing a question like this is based on the fact that multiple research studies have proven that several components of your aerobic fitness are enhanced when you train with low levels of storage carbohydrate or low levels of carbohydrate intake during the exercise session.
Sorry, Wheaties, but it's true: you don't actually have to be a carbaholic to be an endurance athlete.
Now don't get me wrong: there is absolutely no argument that high-carbohydrate intake before an endurance exercise session can postpone fatigue and improve performance. So it's no surprise that the “gold-standard” recommendation from most sports nutritionists is to consume a diet that provides high carbohydrate availability before and during exercise.
But how superior is a high-carbohydrate intake to the polar opposite: eating nothing at all?
A study in the 2010 Medicine and Science in Sports and Exercise Journal suggested the answer to this question when it coined the term “train low, compete high” in response to results that showed untrained individuals achieving better training adaptations and aerobic capacity after 10 weeks of training with low carbohydrate availability, compared to subjects who had high carbohydrate intake before and during exercise.
Another study in the Journal of Applied Physiology showed that trained individuals who performed twice a day training sessions without eating for 2 hours after the first session (thus depleting carbohydrate stores with the first session) experienced a better ability to store carbohydrate, use carbohydrate as energy, and burn fat – with no loss in performance compared to a group that only trained once per day and ate carbohydrates afterwards.
Yet another follow-up study in trained cyclists performed high intensity interval training with no carbohydrate intake showed improved fat utilization and an increase in the enzymes involved in energy metabolism, again, with no loss of performance.
Finally, current research shows that when carbohydrate stores are depleted by almost 50%, there is evidence that there is actually increased stimulus for enhanced enzyme activity in skeletal muscle, which is a good thing, since it means you can more efficiently produce energy from fuel.
And what about eating carbohydrate during training?
Despite the handy sports gel chamber enhanced water bottles on those fancy new bikes, and the tray for your sports gels on the gym's treadmill, as long as the training session is not performed in a carbohydrate depleted state, and does not exceed about 2 and a half hours, there is no evidence to show that avoiding carbohydrate during the session will reduce performance, and there is research that actually shows quite the contrary – no loss of performance!
Whether any of these benefits are due to decreased carbohydrate use or increased fat use is unclear, but there are obviously benefits to going low carbohydrate before and during training.
In summary, if you restrict carbohydrates before, during or after training you may:
#1: Increase activity of the biological mechanisms responsible for building and repairing lean muscle tissue.
#2: Increase ability to preserve and ration valuable carbohydrate stores.
#3: Increase fat utilization during exercise.
#4: Increase the activity of the enzymes responsible for metabolizing carbohydrates during high intensity exercise, such as racing.
In Part II of this series, which will be available at http://www.rockstartriathlete.com on Friday, February 4, you'll learn exactly what happens inside your body when you restrict carbohydrate intake, and get 5 instantly practical ways to cut carbohydrates in your training and racing, along with the advantages and disadvantages of each approach.
If you have questions or comments, please leave them below!