Examination of the Estimated Resting Metabolic Equivalent (MET) in Overweight and Obesity

Abstract

Background: Energy expenditure is commonly expressed in multiples of the resting metabolic equivalent task (MET), with 1 MET estimated to be equivalent to 3.5 ml/kg/min or 0.250 L/min of oxygen consumption. This investigation examined whether the estimated resting oxygen consumption used to express a MET was significantly different than measured resting oxygen consumption in overweight, obese class I, and obese class II subjects. Methods: Forty-five (age: 37.5±10.5, BMI: 32.4±3.5) overweight (N=11), Class I (N=21), or Class II (N=13) obese subjects participated in this study. Resting energy expenditure (REE) was assessed on two separate days. Following a 30-minute supine resting period in a semi- darkened room, REE was assessed using the dilution technique. Data were expressed as relative (ml/kg/min) and absolute (L/min) oxygen consumption. Results: Relative oxygen consumption (3.0±0.6 ml/kg/min, p<0.001) was significantly lower than the reference value for 1 MET (3.5 ml/kg/min), with no difference across BMI categories, but a difference by gender (p=0.002). The reference-MET value over-estimated oxygen con- sumption for females and under-estimated oxygen consumption for males. There was no differ- ence in the measured absolute resting oxygen consumption compared to the reference of 0.250 L/min; however, there were independent gender (p<0.001) and BMI (p<0.001) main effects. Conclusions: These differences between the measured and estimated oxygen consumption rep- resenting 1 MET in overweight and obese adults may have implications with regards to energy expenditure and its assumed impact on body weight regulation. Continued efforts are needed to understand factors that influence metabolism and the variability observed between individuals in energy expenditure.