ectomorph

An ectomorph is a term used in somatotype theory to describe a person with a naturally lean and slender physique. Originally proposed by psychologist William Sheldon in the mid-20th century, ectomorphs are typically characterized by a narrow frame, slender limbs, small joints, and a tendency toward low body fat. People described as ectomorphs often have a fast metabolism and may find it difficult to gain weight or muscle mass, even when consuming a large amount of calories.

Typical traits include a light bone structure, slim shoulders and chest, and longer limbs. Body fat tends to be stored in limited amounts, and gains in strength may occur more slowly than in other body types; however, ectomorphs can and do build significant muscle with appropriate training and nutrition.

Training and nutrition guidance for ectomorphs emphasizes creating a modest calorie surplus and prioritizing resistance training. A program focusing on progressive overload with compound movements (such as squats, deadlifts, presses, and pulls) is common, with a protein intake around 1.6–2.2 grams per kilogram of body weight per day. Carbohydrates and fats are used to meet energy needs, with meals distributed to support training and recovery. Cardio is usually limited to maintain energy balance, though modest endurance work can be incorporated.

Criticism of the ectomorph label notes that somatotypes are oversimplifications; most people are blends of traits and body shape is influenced by genetics, diet, activity, and age. Modern approaches emphasize individualized training and nutrition rather than fixed typologies.