RACIAL DIFFERENCE IN BODY CORE TEMPERATURE BETWEEN PIMA-INDIAN AND CAUCASIAN MEN

A low body temperature is associated with a low metabolic rate for a g iven body size and body composition. These two traits might have been assets in the history of a population subjected to cycles of feast and famine, but became part of an obesity-prone syndrome in our westerniz ed society characterized by plenty of food and a sedentary lifestyle, We tested whether Pima Indians have lower body temperatures than Cauca sians, a trait which might partly explain the high prevalence of obesi ty in this population, Twenty-five Pima Indian (28 +/- 6 yrs, 87.8 +/- 22.8 kg, 29 +/- 9% body fat) and 25 Caucasian (30 +/- 5 yrs, 80.7 +/- 18.4 kg, 22 +/- 11% body fat) men had body core temperatures measured by telemetry for 24 h while in a respiratory chamber, Mean daily body core temperature was 36.93 +/- 0.12 and 36.90 +/- 0.22 degrees C in P ima Indians and Caucasians, respectively, Since body core temperature during sleep (SLBCT) correlated with percentage body fat, a subset of 10 Pima Indians and 10 Caucasians were pair-matched for body weight an d percentage body fat, In this group, SLBCT was lower in Pima Indians than in Caucasians (36.45 +/- 0.10 vs 36.65 +/- 0.27 degrees C; P < 0. 01) and, ethnic group accounted for 20% of the variance in SLBCT (P < 0.01), Surprisingly, the lower SLBCT was not associated with a low met abolic rate and therefore does not seem to play a role in the etiology of obesity in Pima Indians, More studies during cold exposure and/or energy restriction are needed to test whether the maintenance of a low er body temperature might be involved in the pathogenesis of obesity i n some populations.