I am up at 3-5 am and can be so very tired at 7 pm. For me, its the timing. I am a morning person and throughout the day, my energy level gets lower. It has nothing to do with the carb level. There is a separate issue with low carbing and exercise, and you may want to do some research on it. I remember a few body building web sites that were based on the low carb diet and they gave many tips for increasing energy levels that were depleted with exercise.
Started on Sept 26, 2009 Low calorie, low carb, high fat.
My Weight Loss Blog: http://martinimouse.blogspot.com/
My Goal for Hawaii - Spring of 2011