While ecogeographic variation in nasal shape has long been attributed to climatic pressures, recent studies have hypothesized that variation in overall nasal size may be more strongly linked to metabolic demand. This “respiratory-energetics hypothesis” posits that larger individuals with greater metabolic requirements need larger nasal passages to ensure a sufficient intake of oxygen during normal breathing (eupnea). To test this hypothesis, we assessed nasal morphology in conjunction with body mass and basal metabolic rate (BMR) estimates derived from associated postcranial elements for 44 European, 43 Southwest Asian, and 77 Arctic modern human adults. Forty-four 3D-coordinate landmarks were collected from CT scans of each cranium, while postcranial measurements were physically collected from skeletal elements directly associated with each cranium. Body mass and climate-specific BMR were estimated from the postcranial skeleton using established formulae. These data were then employed in multivariate regression analyses to test for statistical associations between nasal morphology and metabolic factors. Results indicate that overall nasal size is significantly correlated with both body mass (Southwest Asia p=0.035; Europe p=0.013; Arctic p<0.001) and BMR (Southwest Asia p<0.001; Europe p<0.001; Arctic p<0.001) in each of the 3 groups. BMR was also found to differentially influence passage height, length, and breadth dimensions, and to particularly influence morphological variation in the anterior nasal cavity and the choanae across the three geographic samples. These results support the basic tenets of the respiratory-energetics hypothesis and suggest that metabolic pressures on overall nasal size are primarily meditated by nasal height and length dimensions, while breadth dimensions are likely associated with climatic pressures for intranasal heat and moisture exchange.