A great article by the one and only:
At the end of your workout, when your body's glycogen stores are low, you have a window of opportunity of around one hour when calories will be used up to 400% more efficiently than at any other time. Food eaten during this period is so vital for recovery that it is often referred to as "free calories."
What to eat matters, however. Sugar is important—perhaps it's the only time it really should be part of your diet. Traditionally, it made up nearly, if not all, of this snack. But recent science shows us that a ratio of 4 parts carbs to 1 part protein with very little fat will provide you with the quickest recovery time, up to 26% better than sugar alone. Fat should be virtually absent here, as it slows the absorption of nutrients (a plus at any other time).
A layman's explanation of the science is this: Your body uses all its stored blood sugar during an intense workout, during which your muscles are broken down. In this depleted state, much damage can be done, so quick replenishment of blood sugar is vital. The quicker you recharge your system, the less damage you'll do and the faster you'll recover. Sugar is absorbed quicker than any other nutrient, which is why you want something high on the glycemic index. And since it's your muscle tissue that is broken down, a little protein added to the mix piggybacks the sugar to jump-start your recovery.
As you may imagine, this is vital for athletes, so you'll find that most sports companies today make a 4:1 recovery formula. Beachbody is one of these, and in my opinion, our Peak Recovery Formula™ tastes by far the best of any on the market. In lieu of this, real food can be used. Something like a small bowl of cereal with nonfat milk or soymilk and a banana will work, or fruit dipped in a little yogurt. Other creative ideas I've seen are sushi rolls (high glycemic white rice with fish) and Gatorade with a scoop of protein powder.