Somatotype
Somatotype describes body build as three separate numbers - endomorphy for roundness and fat, mesomorphy for muscle and bone, ectomorphy for linearity - each rated from about 1 to 7.
Plain English
Patient-Friendly Explanation
Somatotype is a way of describing the shape of a body using three components rather than one number. Endomorphy describes roundness and the tendency to store fat, mesomorphy describes muscle and bone development, and ectomorphy describes linearity - being long and lean. Each component is rated on a scale from about 1 to 7, and the three figures are written together and read separately, never as one large number. A rating of 4-2-2 means endomorphy is the dominant component, so the person tends towards a rounder build, while 1-1-7 is the extreme of linearity. The original idea came from the 1940s, when whole-body photographs were used; it was later standardised so that the rating is calculated from measurements - three skinfold thicknesses, the widths of the elbow and knee, arm and calf girths adjusted for the fat over them, plus height and weight - which makes it repeatable. It is worth being clear about what somatotype does and does not tell you. It is descriptive. Endomorphy does track body fat reasonably well, so a high first number usually means a higher body-fat percentage, but mesomorphy and ectomorphy are weak guides to how much muscle you actually have or to your metabolic health. Two people with identical somatotypes can have completely different blood pressure, blood sugar and risk of disease. Shape is not destiny either: muscle and fat both respond to training and diet regardless of build. Modern clinics rely on waist circumference, body-fat percentage, bioimpedance or DXA scans instead, because those measures have outcome data behind them. Somatotype is still useful in sport and as a friendly way of saying that two people the same weight can genuinely look different.
Medical
Clinical Definition
Somatotype originated with Sheldon in the 1940s, who rated physique from standardised photographs, and was made objective and reproducible by the Heath-Carter anthropometric method, in which endomorphy is derived from the sum of the triceps, subscapular and supraspinale skinfolds corrected for height; mesomorphy from the biepicondylar breadths of humerus and femur plus the corrected arm and calf girths (measured girth minus the overlying skinfold divided by ten) minus height; and ectomorphy from the height-to-weight ratio, with published sex-specific reference values (for example approximately 3.1-5.2-2.1 in young men and 4.1-3.1-2.4 in young women). Each component is reported to a tenth of a point, conventionally plotted as three ratings read separately and located as a point on a two-dimensional somatochart that yields thirteen descriptive categories. In validation work endomorphy correlates well with measured body fatness across populations, whereas mesomorphy correlates only modestly with measured muscle mass and ectomorphy largely reflects skeletal linearity, so the method should not be used as a proxy for body composition. Somatotype is moderately stable across adulthood but is not fixed: training raises mesomorphy and fat loss lowers endomorphy, which is why it also has a history of unfair use in physique-based selection. It has no role in diagnosing obesity, staging risk or guiding treatment - body mass index, waist circumference, waist-to-height ratio, bioelectrical impedance analysis and dual-energy X-ray absorptiometry remain the clinically validated measures - and its current applications are in sports science, kinanthropometry research and patient communication.
Key Insight
Why It Matters
Somatotype just describes the shape you were born with. It does not predict your health or how well you can lose weight - the numbers we actually act on are waist circumference, body fat and how much muscle you are protecting.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: September 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
