Acute modest changes in relative humidity do not affect energy expenditure at rest in human subjects.

Energy expenditure at rest was determined twice in 10 healthy subjects with a 2-d interval at a relative humidity of 32 and 66 per cent respectively. The relative humidity over the 2 d preceding each observation was estimated to be about 32 per cent. The average (+/- s.e.m.) difference between the RMR at a relative humidity of 32 and 66 per cent respectively was found to be 0.3 +/- 1.2 watt. The results presented here justify the commonly used practice of neglecting variations in humidity when reporting on results of observations of resting metabolic rates in apparently healthy subjects.