Basal metabolic rate in human subjects migrating between tropical and temperate regions: a longitudinal study and review of previous work.

A review of the studies of basal metabolic rate (BMR) in human subjects migrating between tropical and temperate countries is presented. Such an analysis showed conflicting results of BMR in tropical migrants when expressed as BMR/kg/d. Much of this confusion may be attributable to experimental design and poor selection of subjects. A longitudinal study of BMR in 18-30-year-old males migrating for the first time from a tropical to a temperate country (the UK) was undertaken to address disparities seen in the earlier reviewed work. BMR was measured in tropical migrants and their temperate resident peers serially from 2 to 3 weeks post-migration to up to 6 months later, making advances on previous studies which did not measure BMR so promptly post-migration, or conduct serial measurements. The tropical migrants recruited in this investigation were of high socioeconomic status and well nourished. BMR/kg/d was similar in tropical migrants and temperate residents, there being no time trend in either group through the course of the study. The BMR of both groups was similar to that of populations born and resident in temperate regions, in contrast to the lower BMRs of born and resident tropical peoples reported in the literature. It is suggested that these lower BMRs are the result of a different relationship of BMR with body weight in individuals who are undernourished and/or of low socio-economic status, the corollary of which is a lower body weight, stature and body mass index.