You should eat simple carbs after a workout for several reasons. First, simple carbs get into your system very quickly. Second, simple carbohydrates can elicit a very
strong surge of the anabolic hormone insulin. Aside from the overt anabolic effect, insulin facilitates amino acid and glucose transport into the muscles. Insulin is
also involved in a mechanism known as potassium homeostasis, or stabilization of the amount of potassium in blood and muscles.
When you exercise, large amounts of potassium are dumped from the muscles into the blood. The insulin released after ingesting simple carbs will pump sodium out of muscle cells and pump the potassium back in, by way of the sodium-potassium-ATPase process. Simple carbs help drive this correcting mechanism.
Many people try to inhibit the catabolic state by taking supplements that suppress Cortisol release, but this is not the best strategy for mass gains. If bodybuilders inhibit catabolism, they won't get the quality of gains that they're seeking. They have to clear their muscles of garbage (through catabolism) for the growth (through anabolism) to work most effectively. The type of catabolism that occurs after stressing a muscle is much different from the catabolism that occurs in fasting and starvation. Exercise-derived catabolism is an important part of the total anabolic process. It's better to drive the process forward rather than try to inhibit something that occurs naturally. And that's what simple carbohydrates help your body do.