^ I've had the worst case of 'bacne' and acne on my face during my bulking days... Which I was ingesting copious amounts of dairy and wheat. I simply attributed it to just bad skin for years until I came across gluten intolerance. It's important to note that a gluten intolerance often times coincides with dairy (casein) intolerance. I don't have full blown celiac, but I definitely do have an intolerance to products with gluten.
It wasn't only the bad skin, but also having bouts of fatigue, being lethargic, and cloudy thinking. Gluten intolerance is still a gray area in nutrition, as it is 'relatively new' and pundits are still in disagreement.
But in my personal experience, I have seen DRASTIC differences in eliminating gluten completely from my diet.
I literally never get breakouts anymore or random fatigue, thinking is clear, performance in training/lifting is great, and I even feel more calm. Dare I say that it even cured my bouts of depression.
I do occasionally (maybe monthly) indulge in gluten (a pita bread with my middle eastern food, or a beautiful brick oven pizza), but the effects are felt almost immediately.
The only pre-workout I ever sometimes use is a cup of coffee. But for a week after eating gluten, I notice a distinct difference in not only energy, but my motivation on the mats or in the gym. It is then I can see why so many, who are perhaps unaware of a gluten intolerance or other food allergies, are so adamant about getting their pre-workout drink in before every session. Because I say that if you need a substance to get your ass to the gym, you're in there for the wrong reason, but I digress.
Of course, to each his own.