To investigate whether resting metabolic rate (RMR) differs between Caucasian and Polynesian women. Cross-sectional comparison. Eighty-two (42 Caucasian, 40 Polynesian) healthy women aged between 18 and 27 y. RMR (indirect calorimetry) and body composition (fat-free mass and fat mass derived from oxygen-18 dilution measurement of total body water). RMR was similar in the Caucasian (6956 +/- 1291 (s.d.) kJ/d) and Polynesian (7125 +/- 1290 kJ/d) groups while fat-free mass was significantly lower in the Caucasian group (45.3 +/- 6.8 vs 51.0 +/- 6.4 kg, P < 0.002). After adjustment for fat-free mass and fat mass, RMR was lower in the Polynesian than the Caucasian groups (6783 +/- 904 vs 7281 +/- 901 kJ/d, P = 0.023). The significantly lower relative RMR observed in Polynesian compared to Caucasian women may predispose Polynesian women to eventual onset of obesity.