Twenty-four-hour energy expenditure and resting metabolic rate in obese, moderately obese, and control subjects

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Abstract
Twenty-four-hour energy expenditure (24-EE), resting metabolic rate (RMR) and body composition were determined in 30 subjects from three groups; control (103 ± 2% ideal body weight, n = 10), moderately obese (129 ± 1% ideal body weight, n = 6), and obese (170 ± 5% ideal body weight, n = 14) individuals. Twenty-four EE was measured in a comfortable airtight respiration chamber. When expressed as absolute values, both RMR and 24-EE were significantly increased in obese subjects when compared to normal weight subjects. The RMR was 7592 ± 351 kJ/day in the obese, 6652 ± 242 kJ/day in the moderately obese, and 6118 ± 405 kJ/day in the controls. Mean 24-EE values were 10043 ± 363, 9599 ± 277, and 8439 ± 432 kJ/day in the obese, moderately obese, and controls, respectively. The larger energy expenditure in the obese over 24 h was mainly due to a greater V̄O2 during the daylight hours. However, 92% of the larger 24-EE in the obese, compared to the control group, was accounted for by the higher RMR and only 8% by other factors such as the increased cost of moving the extra weight of the obese. The higher RMR and 24-EE in the obese was best related to the increased fat free mass.