Spinach provides heaps of vitamins, and has less than a dozen calories per serving. One cup of spinach offers 5 percent of the iron you need daily, which is great news because not getting enough of the mineral can result in exhaustion. To make it a meal, serve spinach as a salad with garbanzo beans and some balsamic vinegar. For a morning workout, make a spinach and egg white scramble with a slice of whole wheat toast.