An ectomorph is one of the three primary body types in the somatotype classification system, which also includes mesomorphs and endomorphs. Ectomorphs are characterized by a slim, lean physique with narrow shoulders and hips. They typically have a fast metabolism, making it difficult for them to gain weight or muscle mass. People with an ectomorphic body type often have long limbs and little body fat. This body type is common among athletes in sports that require speed and agility, such as long-distance running or cycling. Ectomorphs may need to focus on strength training and a calorie-rich diet to build muscle effectively.