Mark Sisson has a great extended piece on the “low carb flu,” something most people experience when eliminating grains and sugars from their diet. I recommend you read the whole thing.
However, transitioning from a carb-based diet to a fat-based one – while ideal – is not always practical for those of you doing heavy endurance training. Per Mark:
Keep in mind also that people in low carb transition can genuinely shortchange their physical needs when they aren’t eating enough fat or when they’re pursuing high intensity exercise routines lasting over an hour, which send the body’s glycogen stores into a nosedive to the ground. I hear this from CrossFitters and P90Xers who insist on maintaining their daily high intensity while transitioning to Primal eating.
Bottom line, it’s almost impossible to completely “go primal” while training for that big marathon or triathlon. But then again, you shouldn’t really be doing all that chronic cardio anyway, right?
Yeah not a big fan of the Primal/Paleo diet. I like the idea of rearranging the food pyramid to include more fruits and vegetables. It also I think gives great short term benefits in weight loss and can be good for recovery days based on its high protein and low sugar. But I don’t buy into it for endurance training. My view on nutrition is more along the lines of get everything in its most natural state (meaning not processed), use the whole grain and prepare it correctly. I have many views on nutrition though haha.