This allows for carbohydrates to be consumed before intense workouts. This works for short term high intensity exercise, 30-60g carbs taken 30 mins to one hour before exercise is recommended. When in ketosis the body is using fat for energy however energy from glucose is accessed more rapidly, hence why many athletes who are already in ketosis will choose to add simple unrefined carbs like fruit or complex carbs like root vegetables before they work out. Its worth noting here that some of the best minds in the field like Professor Tim Noakes has changed his stance on this and now uses fat to fuel his intense exercise, admitting that his stamina has increased tenfold. When you start a ketogenic lifestyle you will find lack of strength and endurance initially. You must choose whether to continue fuelling with carbs or try to push through the drawbacks to become better, stronger and more fuel efficient than you were previously.