A Re-examination of the Metabolic Equivalent Concept in Individuals With Coronary Heart Disease

In Brief OBJECTIVE: The metabolic equivalent (MET) is a commonly used method of quantifying the energy cost and intensity of physical activity. Recent studies have questioned the accuracy of the well-accepted value of a MET of 3.5 mL O2 · kg−1 · min−1. The goal of the present study was to compare the traditionally accepted value for 1 MET to direct measures of resting metabolic rate in a group of stable individuals with coronary heart disease (CHD). METHODS: The primary cohort consisted of 109 (60 men and 49 women) subjects with documented coronary heart disease and a body mass index ≥25 kg/m2. Measurements included indirect calorimetry, body composition, and exercise capacity (peak oxygen uptake [VO2]). In a substudy of 17 (10 men, 7 women) normal weight subjects (body mass index <25 kg/m2), metabolic rate in the seated position was also measured. RESULTS: Mean resting value for 1 MET was a VO2 value of 2.58 ± 0.4 mL O2 · kg−1 · min−1 for overweight subjects measured in the supine position and 2.84 ± 0.59 mL O2 · kg−1 · min−1 for normal weight individuals measured in the seated position. Caloric expenditure value was 0.74 ± 0.12 kcal · kg−1 · h−1 rather than the expected value of 1 kcal · kg−1 · h−1. Values were similar between men and women. Women on beta-blockers had a lower resting metabolic rate (2.47 ± 0.27 vs. 2.71 ± 0.38 mL O2 · kg−1 · min−1) (P < .05) than women not on beta-blocker therapy, whereas there was no effect of beta-blockers in men. CONCLUSIONS: Findings confirm recent studies of otherwise healthy individuals and indicate that the average resting metabolic rate in subjects with coronary heart disease is 23% to 36% lower than the widely accepted value of 3.5 mL O2 · kg−1 · min−1. Results demonstrate the limitation of the convention of expressing energy expenditure in multiples of an assumed constant. The metabolic equivalent (MET) is a commonly used method of quantifying the energy cost and intensity of physical activity. The goal of the present study was to compare the traditionally accepted value for 1 MET to direct measures of resting metabolic rate in individuals with CHD. Findings concur with recent studies of otherwise healthy individuals and indicate that the average resting metabolic rate (MET) in subjects with coronary heart disease is 23% to 36% lower than the widely accepted value of 3.5 mL O2 kg−1 min−1. Our results demonstrate the limitation to the convention of expressing energy expenditure in multiples of an assumed constant.