Energy expenditure in sago processing by women in the Purari delta of Papua New Guinea

Palm sage is an important staple food for populations living at low density, and on marginal lands in Papua New Guinea and elsewhere in Melanesia. The exploitation of palm sage is a highly efficient means of provisioning a community with dietary energy, but has been shown to be an energetically costly activity. However, a previous estimate of the energy cost of sage making was not based on the measurement of oxygen consumption, but on an indirect prediction of it, from estimates of energy expenditure at given heart rates obtained from another study in Papua New Guinea, and controlled for body weight. In this study, the energy expenditure in sage processing among a small group of Papuan women was determined using oxygen consumption measurements in the field and compared with estimates obtained by predicting from heart rate using regressions of heart-rate against energy expenditure obtained for each woman in the study, and obtained from literature values. The energy expended in adzing sage and making sage were shown to be similarly high by the oxygen consumption method, but in neither case as high as the value obtained by predicting from heart rate and energy expenditure values given in the literature. In this first report of energy expenditure in sage processing determined by direct measurements of oxygen consumption, energy expended in sage making is shown to be lower than previously estimated.