Many young athletes are eating plenty of protein and still not eating enough. Relative Energy Deficiency in Sport, or RED-S, happens when an athlete takes in too little energy to support both training and normal body function. It can affect growth, bone health, hormones, mood and performance. Stacy Bates, MS, RDN, explains why she’s seeing more RED-S in young male athletes, how a heavy focus on protein can crowd out the carbohydrates they need, and the warning signs parents and coaches should watch for.