A couple of points that need to be made here:
Although insulin has been vilified in many circles, it is fundamental to the survival of the organism. If a given food does not produce an insulin response, then it cannot be assimilated by the body. The extreme example of this is Type I diabetes where the pancreas, due to a congenital defect is unable of producing insulin. Unless treated, type I diabetics literally will starve to death irrespective of the quantities of food that they ingest.
So, when you diligently take your whey protein after your workout, you are explicitly relying on an insulin response to drive those amino acids into your muscles. Try to keep in mind what is meant by that “window of opportunity” you refer to. This is that 90 minute or so period immediately after exercising where the muscles have increased insulin sensitivity. Note, however, that insulin sensitivity means nothing if in your bloodstream there is 1) no insulin, and 2) no nutrients. So, your whey intake dovetails quite nicely with these requirements. It provides amino acids and promotes an insulin response to mediate the transport of these amino acids into the muscle cells.
After 90 minutes, muscles return to their relatively insulin insensitive state, and the “window of opportunity” closes. The only tissues that remain insulin sensitive are the adipose tissues, and that is not something that we want to be feeding.
When it comes to growth hormone, I would need to know what it is that you are trying to accomplish by raising GH levels? If it is increased release of free fatty acids from your adipose tissue, then that is brilliantly accomplished by fasting. If you are after muscular growth, ie increased protein synthesis, then you are better off trying to increase your testosterone levels and letting the GH take care of itself. Heavy exercise in and of itself ( within reason, don’t overtrain yourself into the ground ) will serve to boost your anabolic hormones.
Read more: Insulin Index | Mark's Daily Apple