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 semidarkened 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 consumption for females and under-estimated oxygen consumption for males. There was no difference 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 representing 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.