The effect of eating carbs strategically is simple. Any carbs consumed raise your insulin level which normally leads to increased energy levels or storing fat. Here is a short video in which Jennifer Elliott, an Australian dietitian, explains such effects of insulin. However, post-workout carbs may have an anabolic effect and stimulate muscle growth (depending on the workout and intensity). This doesn't mean that you need to eat carbs if you want to gain muscles. Unless you aim for a significant muscle gain, post-workout carbs are not needed.