Carbohydrates are a type of macronutrient – a nutrient that has caloric value to it. Other macronutrients include lipids (fat), protein. Types of carbohydrates include starches, sugar, or fiber. Excess carbohydrate consumption in the form of sugar (especially fizzy drinks) and/or high glycemic foods like white bread, white rice, sweets, white potato along with lack of exercise is what is linked to increased prevalence of obesity (1) Each macronutrient has a different responsibility unique to its metabolic processes. Certain organs in your body are capable of metabolizing only carbs for fuel, which include your brain, red blood cells, and kidneys. Additionally, your muscles store carbs in long branches and chains in the form of glycogen. Glycogen is the fuel your muscles use when exercising, particularly at high intensities or during intermittent exercise. During your workout, your muscles are under high physical demand and require appropriate fuel to be able to perform the task at hand. Said fuel is in the form of glycogen. However, if you don’t have the appropriate carbohydrate stores, your body will begin to tap into other fuel sources, which includes your fat and protein storage. If you perform high intensity exercise on a regular basis (CrossFit) without the proper carbohydrate intake, you compromise your ability to gain muscle or fortify the existing muscle. As a result, you essentially burn through fat stores and begin to “eat away” at the muscle you already have, as your muscles’ alternative to glycogen (2) The issue with not eating enough carbohydrates for exercise lies in your body’s inability to build and strengthen lean tissue. Without adequate glycogen stores you aren’t able to refuel or rebuild the tears in your muscle fibers naturally caused by exercise. As a result, that rule of “muscle burning fat” doesn’t apply since you’re losing your muscle.. There goes your lean and toned body! Carbs are still your friend even if you don’t want to be lean and toned! Adequate glycogen stores are a critical component in muscle synthesis and reestablishing those muscle tears. It has been demonstrated that carbohydrate intake enhances one’s athletic ability and performance simply because you’ve giving your muscles the right fuel for the right task (3) The research is quite clear that if you start your next training session with low or sub-optimal glycogen status, you’ll significantly reduce your capacity to work and your performance will suffer. A recent study of athletes who consumed only 40% of their total calories as carbohydrates and performed “two-a-day” training sessions suffered a significant decrease in their performance during the 2nd session because they did NOT adequately replenish muscle glycogen stores (4) Short-term symptoms of inadequate glycogen repletion include fatigue, reduced work capacity during training, poor recovery and extended delayed onset muscle soreness (DOMS). Long-term symptoms are pronounced fatigue, reduced strength levels and increased muscular weakness. The best way to replenish glycogen after training is to consume high-glycemic index (GI) carbs. High GI carbs enter the bloodstream quickly, allowing you to rapidly replenish glycogen stores in the first 30-60 minutes after training, when glycogen synthase enzyme activity is elevated and allows for optimal replenishment (5) Root vegetables make a great post-workout carb choice such as sweet potatoes, plantains, carrots, beets, parsnips, etc or if you’re on the run adding dextrose to your protein shake is a great way to replenish glycogen stores. Carbs directly replenish glycogen stores and after exercise your capacity to soak up carbs and top up glycogen is heightened. Research shows that if you wait several hours post-training you will reduce your glycogen repletion rate by as much as 50%! (6) Not consuming enough carbs after exercise can also exacerbate inflammation, depress immunity, and lead to prolonged muscle soreness (7) References 1. Lugwig DS. Dietary glycemic index and obesity. The Journal of Nutrition. 2000:280-283. 2. Rennie MJ, Bohe J, Smith K, Wackerhage H, Greenhaff P. Branched-chain amino acids as fuels and anabolic signals in human muscle 1 – 2. The Journal of Nutrition. 2006;36.1:264-272. 3. Costill DL, Sherman WM, Fink WJ, Maresh C, Whitten M, Miller JM. The role of dietary carbohydrate in muscle glycoen resynthesis after strenuous training. Am J Clin Nutr. 1981;34:1831 – 1836. 4. Ivy JL et al. Muscle glycogen storage after different amounts of carbohydrate ingestion. J Appl Physiol. 1988 Nov;65(5):2018-23. 5. Jentjens R, Jeukendrup A. Determinants of post-exercise glycogen synthesis during short-term recovery. Sports Med. 2003;33(2):117-44. 6. Jentjens R, Jeukendrup A. Determinants of post-exercise glycogen synthesis during short-term recovery. Sports Med. 2003;33(2):117-44. 7. Flakell PJ et al. Postexercise protein supplementation improves health and muscle soreness during basic military training in Marine recruits. J Appl Physiol 2004;96:951-956.