We have been living in a low carb revolution, but thank goodness it is slowly emerging back to normal. Dr. Atkins was one of the for fathers of this phenomenon. One cannot leave out Barry Sears of The Zone fame, either and somewhat more recently, The South Beach diet, and Paleo diet, for the continued population growth of the carb-limiting fanatics. They are still out there, I come accross it in my practice everyday. But with the emergence of more endurance athletes, and triathlon, there is more of a focus on a balanced amount of good carbs with an appropriate amount of good protein, for good reason.
Books like Dr. Atkins, The Zone, Good Carbs, Bad Carbs, and the South Beach Diet claim that we can blame the obesity epedemic in America on carbohydrates. These low carb philosophies claim that certain carbohydrates cause a quick rise in blood sugar which in turn raises insulin levels. They further claim that insulin leads to weight gain by either being a promoter of stored fat or by reactive lowered blood sugar level, stimulating hunger, and thus encouraging over consumption of calories. Unfortunately, it is in our culture to grasp on to quick fixes. Granted, there are metabolic reasons why one can lose “weight” on high protein (low carb) diets, which has thus claimed this carb-restriction revolution. Publishers and marketers knows what sells resulting in the low carbohydrate diets being popularized without detailed evidence of their efficacy or long term safety and athletes are getting caught up in the low carb frenzy. The quick weight loss from limiting carbohydrates is just that – a quick fix. Athletes however, should really take note how surprisingly few scientific-based studies have shown how different carbohydrates affect weight loss. Furthermore, there is no clear evidence that a rise in blood sugar that comes from eating carbohydrates leads to an insulin increase, or that higher insulin causes people to overeat.
Although these quick fixes, regardless of the lack of scientific knowledge, are welcomed amongst significantly overweight, sedentary people, they were not designed to supply the nutrition for active people who need to support exercise and training. While low carb, quick weight-loss results are welcomed, athletes should regard these same “quick fixes” as lost energy. The initial and rapid weight loss from low-carb diets can be explained as glycogen depletion and loss of water weight. Glycogen (immediate source of energy in muscle) in the body is stored with 3 grams of water. So, each gram of carbohydrate energy, then, accounts for 4 grams of body weight. By limiting carbohydrates, glycogen will be used as energy first. For an athlete, glycogen depletion can take as little as a few hours, whereas for a sedentary person, glycogen depletion can take up to a few days.
Once glycogen stores are depleted, the body seeks out fat and protein sources for energy. First it turns to protein, converting amino acids from muscle tissue into glucose in the liver. This process is relatively slow and can produce only enough carbohydrate to fuel the brain and nervous system. Without ingestion of additional carbohydrate, ketone bodies (byproducts of fat metabolism) are produced and released into the bloodstream. A state of ketosis is induced. Ketosis is explained as an increase in ketone levels. Ketones in the bloodstream does suppress the appetite, but is also be accompanied by undesirable side effects, such as nausea, headaches, fatigue, and breath that smells like ammonia. Athletes on low-carb diets have difficulty sustaining even moderate intensity workouts of 50-65% of max heart rates when ketone levels are elevated.
In summary, the low carb philosophies demand a restriction of the very elements that athletes need to powers muscle with energy – digestible, usable, and absorbable carbohydrate. Carbohydrate is fuel for muscles that can be burned quickly, providing the power for acceleration and high performance.
1.Advances in Sports Nutrition. Journal of American Medical Association. JAMA 2003;289:1837-1850.
2.How net carbs can hurt athletes. Ashley Kipp. Published on trainright.com, accessed October 2004. 3.Weighing the Diet Books. Nutrition Action. January 2004, volume 31:1.