This is a JB question. If you read "massive eating" he talks about it. Link's down in the "Are you a Beginner II" thread.
Insulin is a double-edged sword. It is the most anabolic hormone in the body, but if it runs rampant you get excess body fat and, at worst, diabetes, heart disease, and all sorts of metabolic disorders.
The idea behind the P+C and P+F but not C+F meals is to maximize insulin while minimizing circulating fatty acids in the blood. (And vice versa--when I do eat fats, I don't want a big insulin rush. But you need fats to produce testosterone and keep everything running smoothly.)
I.E. if I were to eat some french fries and a Coke, I'd be getting a massive load of crap saturated fats and trans-fats. The Coke would pop my blood sugar up at the same time, and I'd get a massive insulin response.
The insulin would then proceed to suck all the nutrients out of the blood, shuttling them to the cells. Since I have nothing but crap fats in my blood, I get crap fats shoved willy-nilly into my cells. End result after rinsing and repeating? I become a corpulent douchebag sitting on the couch and watching daytime talk shows.
Now, let's flip that scenario. P+C, like Surge. Same insulin response, but this time, I have quality protein, amino acids, and quite possibly creatine in my blood. Insulin does its thing, and whammo, instead of crap fat, my cells get a nice protein snack.
Now, if you timed this right (i.e. early morning or post-workout) you can add to this effect because your cells are "hungry". (That is, you've used up some of the glycogen to exercise, or while you were sleeping). This way your body absorbs more of the carbs without converting them to fat. (If your muscles are full and you eat a P+C meal, you get "glycogen spillover" and the excess will be stored as fat.)
Hope that answers the question.
Dan "I ain't got no biochem degree, though, so I mighta oversimplimafied some thangs" McVicker