Body mass index, ageing and differential reported morbidity in rural Sarawak

Classifications of adult low energy nutritional status based on the Quetelet or body mass index (weight/height2) have often assumed independence of age and sex. This paper reports findings of a study of 447 men and 564 women aged over 18 years and belonging to the Iban tribe of central Sarawak, East Malaysia. BMI and fat-free mass fell markedly in both sexes, and fat mass in women but not men, after about 40 years of age. In men over age 40, and women aged 18-40, BMI was sensitive to reported morbidity. For subjects aged over 40 years, BMI was related to morbidity independently of age effects in men, and to age alone in women. These findings suggest that the functional significance of low BMI differs between the sexes and with age.