It is highly recommended by athletic professionals that you eat after any type of exercise — preferably within 45 minutes. Golf is no exception. The bottom line is this: When you expend energy by exercising — even while playing golf — you need to consume extra energy to fuel the activity as well as recover from it. Within the first 45 minutes post-exercise, there is a "metabolic window." Enzymes that replenish muscles are at their highest levels. Also, insulin, which rebuilds protein stores, is at peak levels. So eating a carb-and-protein mix (peanut butter sandwich, yogurt with fruit, bagel with cream cheese, or a handful of nuts) at this point will maintain muscle, replenish glycogen stores and reduce the amount of fat your body stores.
While eating healthily won't help you cut your golf handicap overnight, all golfers can benefit from making some changes to their diet on and off the course.