J L Seale

Energy expenditure measurements in relation to energy requirements

Long-term good health for weight-stable adults requires balance between energy intake (EI) and energy expenditure (EE). Both EI and EE measurements can be used to estimate energy requirement. Results from studies conducted at Beltsville Human Nutrition Research Center in which two or more methods were used to measure EE are compared to determine relative differences in measurement techniques. Comparison of EI estimated from dietary intake records (7 d minimum) with EI measured in 12 controlled feeding studies (45 d minimum) in 266 subjects indicated that diet records underestimate energy requirement by 18%. Comparison of EE measured in a room calorimeter and by doubly labeled water (2H(2)18O) in nine subjects showed no significant difference between methods within the calorimeter environment (1.6 +/- 2.6%) but free-living EE measured by 2H(2)18O was greater (13.2 +/- 7.1%) due to physical activity. Comparison of metabolizable energy (ME) intake, 2H(2)18O, and direct or indirect calorimetry in four subjects indicated no difference between ME and EE measured by 2H(2)18O (-1.0 +/- 1.3%) or between direct and indirect calorimetry (0.6 +/- 0.9%); however, free-living EE measured by 2H(2)18O was greater than the value calculated by calorimetry (15.3 +/- 5.0%). Each method has associated limitations that include availability, accuracy, precision, and cost. Appropriate application and interpretation of results for all methods are essential.

Energy expenditure by indirect calorimetry in premenopausal women: variation within one menstrual cycle☆☆☆

Energy expenditure in relation to the menstrual cycle was determined by indirect calorimetry in premenopausal women. For each subject, three measurements were made within a single menstrual cycle. Energy expenditure measurements coincided with the subjects expected hormonal fluxes of estradiol and progesterone: menstrual phase-both hormones at basal levels; follicular phase-elevated estradiol; and luteal phase-elevated progesterone. In experiment I, resting energy expenditure of 14 women was determined for 1 hour using a canopy system for calorimetry; in experiment 2, 24-hour energy expenditures of 12 subjects were measured in a room-size calorimeter. Blood from fasted (12 hours) subjects was collected following measurements of energy expenditure and analyzed for serum estradiol-17B and progesterone by radioimmunoassay. In experiment 1, resting energy expenditure did not differ within one menstrual cycle; neither estradiol nor progesterone affected resting energy expenditure. In experiment 2, 24-hour energy expenditure was significantly lower (P < 0.013) during the follicular phase when compared with the menstrual (−3.8%) and luteal (−4.9%) phases. Lowered 24-hour energy expenditure during the follicular phase may in part be due to a decrease in spontaneous activity and exercise. Energy expenditure during sleep, an indicator of metabolic energy expenditure, was significantly greater (P < 0.0001) during the luteal phase than during the menstrual (+6.7%) and follicular (+5.4%) phases; this was a reflection of increased progesterone (P < 0.0001). Twenty-four hour energy expenditure (mean ± SEM) during the menstrual, follicular, and luteal phases was 8.86 ± 0.26, 8.52 ± 0.22, and 8.96 ± 0.21 MJ/d, respectively. Corresponding values for energy expenditure during sleep were 5.49 ± 0.09, 5.56 ± 0.10, and 5.86 ± 0.11 MJ/d. The menstrual cycle is a significant contributor to variation in energy expenditure through progesterone-mediated increases in metabolic rate. Variation in metabolic energy expenditure was detectable when the contributory components of 24-hour energy expenditure were measured.