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

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Abstract

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.

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