Science Figures Interpreted and Analyzed by RealClearScience
Those who exercise regularly have undoubtedly heard the notion of a post-workout "window of opportunity." The idea here is that the exerciser should consume some sort of food or dietary supplement with a fair amount of protein or carbohydrates immediately following a workout. Doing so will supposedly yield added benefits such as improved body composition (more muscle, less fat) and an enhanced ability to recover and be ready for another workout.
Over the years, marketers have stressed this idea, running campaigns touting the notion that if you don't consume their product immediately before, during, or after your workout, then your physical exertions are "wasted."
Seeking to determine whether or not such a "window of opportunity" actually exists, health scientists Alan Aragon and Jon Schoenfield conducted a thorough review of the available literature. They discovered that evidence-based support is "far from definitive."
Serious athletes and those interested in significant muscle growth were the only groups for which the potential benefits for post-workout nutrition could not be dismissed, they found.
While a sufficient amount of protein and carbohydrates are needed to repair damaged muscle tissue and refill muscle glycogen stores following a workout (muscle glycogen is stored energy used to fuel moderate to high intensity exertions), the reviewers found that these requirements could easily be sated with a balanced diet and consuming a meal one or two hours before exercise.
Source: Aragon and Schoenfeld (2013) Nutrient timing revisited: is there a post-exercise anabolic window?: post-exercise nutrient timing. Journal of the International Society of Sports Nutrition, 10:5 doi:10.1186/1550-2783-10-5