If you compare cultures who live extremely low carb, like the early Native-Americans, Alaskan Inuits or Australia's Aborigines to other cultures, like modern America You might draw this conclusion: If you are accustomed to sustaining physical activity with a minimal amount of carbs over a great length of time, you are okay. But, if you have lived a life where carbohydrates were the body's main energy source, it is difficult to achieve the same stamina level without more carbs in the system, even if one changed to the low carb woe.