Skinfold Thickness

Skinfold measurement uses calipers to measure the thickness of a double fold of skin and subcutaneous fat at defined sites. Because about half of body fat lies under the skin, the sum of several skinfolds can be used to estimate total body fat through published prediction equations.

It is inexpensive and portable. Its accuracy depends on the skill of the observer.

Usage. It is used in nutritional assessment, research, sports medicine, and in monitoring children and patients with malnutrition.

Common sites. Triceps (midpoint between acromion and olecranon, at the back of the arm), biceps, subscapular (just under the lower angle of the scapula), and suprailiac (just over the iliac crest).

Preparation and technique. The skin and fat are lifted with the thumb and index finger, away from the muscle. Calipers are applied about 1 cm from the fingers, and the reading is taken after 2 to 4 seconds. Measurements are taken on the right side, repeated at least twice, and the mean is recorded. Repeat measurements should agree within 1 to 2 mm.

Contraindications and precautions. Oedema, extreme obesity and skin conditions at the site limit measurement.

Interpretation.

• The triceps skinfold is compared with age- and sex specific reference values. Values under the 5th centile indicate depleted fat stores.
• Together with mid-upper arm circumference, the triceps skinfold is used to calculate arm muscle area, an index of muscle mass.
• The sum of several skinfolds is entered into a prediction equation to estimate body fat percentage.

Causes of low skinfolds. Malnutrition, chronic illness, malignancy, and high levels of athletic training.

Causes of high skinfolds. Obesity, hypothyroidism, and Cushing syndrome.

Critical values and findings needing immediate action. Severe depletion of fat and muscle stores with weight loss warrants prompt nutritional intervention.

Limitations and artefacts. Inter-observer differences are substantial. Compressibility of fat varies with hydration and age. Equations apply best to the populations in which they were derived.

Follow up tests. Mid-upper arm circumference, bioelectrical impedance analysis, DEXA, and serum albumin and prealbumin.

Special groups. In children, skinfolds are interpreted with centile charts. In older adults, fat shifts from limbs to trunk, which limits the value of limb sites.