Arm fat and muscle areas in infancy.

Growth of arm muscle, fat and water areas were evaluated longitudinally in a prospective study in 81 infants from birth to the age of 12 months. The percentage of arm fat area v the cross sectional upper arm area increased at the age of 15 days with a peak peak at the age of 6 months while arm muscle area increased progressively throughout the year. As arm water area represented only 1% of cross sectional upper arm area, calculations of arm fat and muscle areas can be carried out from measurements of mid arm circumference and tricipital skinfold at 15 seconds. Percentiles are presented for the upper arm fat and muscle areas, which can be used as index for the infants' nutritional state.