Sports nutrition: do you really need it?

Protein bars, electrolytes, energy gels: sports drinks and other snacks are multiplying on shop shelves. And elite athletes are by no means the only ones to consume them; amateurs are also fond of them. These products are often swallowed with the aim of doing one's body good and improving performance. But do these products live up to their promises? Are they really a plus for those who train moderately?