Thermal and metabolic responses of women with high fat versus low fat bodycomposition during exposure to 5 and 27 degrees C for 120 min

Background: Men with high fat body composition maintain higher core tempera tures, and lower aerobic metabolic rates than their low fat counterparts th us, verifying the insulatory benefit of body fat. Females, on average have more body fat and less muscle mass than males, and may maintain rectal temp erature (T-re) at a tower energy cost. Methods: The present investigation d ichotomized female subjects by percent fat (low fat; n = 3, LF = 19.2 +/- 3 % vs. high fat; n = 4 HF: 29.9 +/- 3%) to elucidate the thermal and metabol ic responses during acute exposure to 5 and 27 degrees C air for 120 min. A n ANOVA was used to examine the following: T-re (degrees C), mean skin temp erature (T-sk; degrees C) oxygen consumption (V) over dot O-2; ml.kg(-1).mi n(-1) and tissue insulation (I; degrees C.m(2).W-1). For T-re, a significan t fat X time interaction (p < 0.05) was demonstrated at both 5 and 27 degre es C, whereby T-re tended to be lower in the LF group than the HF group, (V ) over dot O-2 at 5 degrees C demonstrated a main effect for time only. For I, a main effect for time was noted at 5 degrees C. Also for I, a trend (p = 0.06) toward a main effect of fat during exposure to 5 degrees C was not ed while at 27 degrees C a main effect (p < 0.05) was demonstrated. Results : From this data it appears that under these conditions, the HF group demon strated higher T-re and I values than their LF counterparts that was not ac companied with a differential response with respect to aerobic metabolic ra te. Thus, the impact of body composition on energy expenditure to maintain T-re differs between LF and HF males and females.