Stability of Basal Metabolic Rate Over Selected Days of the Menstrual Cycle

Abstract

Because of the relatively large cyclical changes, studies examining the effects of factors other than menstrual cycle on energy expenditure are conducted predominantly in men. Examination of data from previous studies examining the entire menstrual cycle suggested that basal metabolic rate was relatively stable on days 5, 6, and 7 after the onset of menses. (3.5) We conducted a pilot study to reexamine the stability of BMR over those three days.Sixteen women between the ages of 23 and 40 (32 k 5 years, mean f SD) were recruited to represent a wide range of fatness. Body mass index ranged from 18.3 to 53.1 kg/m2 (31.0 k 11.2, mean k SD) with fatfree mass (FFM) ranging from 37 to 79 kg (53 f 12, mean f SD). Subjects were excluded if they had attempted weight loss within 6 months of study entry. All were very sedentary, premenopausal, in apparent good health, were not diabetic, did not smoke and did not use oral contraceptives. All subjects reported having regular menstrual cycles and ovulation was assumed to occur on day 14.Subjects were admitted to the General Clinical Research Center on day 4 of menses over two consecutive menstrual cycles, and basal metabolic rate was measured on days 5, 6, and 7. Subjects spent the night in the GCRC but were allowed to maintain their usual activities during the day. Participants were given an individually determined weight-maintaining diet (estimated at 1.3 x BMR derived from age, sex, height and weight tables) with 50% of energy from carbohydrate, 15% from protein, and 35% from fat. Potassium and sodium intakes were kept constant. Subjects were encouraged not to lose or gain weight between admissions.Subjects were asked to abstain from all vigorous physical activity the day before testing, to fast after dinner the night before testing, and to be in bed at 2300. On days 5, 6, and 7, subjects were awakened at a standardized time. After voiding, weight and height were measured and immediately afterwards they returned to bed and rested quietly for thirty minutes.Energy expenditure was measured using an opencircuit, canopy-ventilated, indirect calorimeter (DeltaTrac, Sensormedics Corp., Yorba Linda, CA). The subjects remained motionless and awake during the measurement period. Each study period was preceded by a 10 yinute stabilization period after canopy placement. Energy expenditure was calculated for each oneMnute interval using the Weir equation (7). The BMR values were calculated as the mean value over 30 minutes of continuous measurements.Body composition was assessed in the morning of the last study day (day 7 of the second cycle) by hydrostatic weighing with in-tank determination of residual lung volume using a closed circuit oxygen dilution technique. Fat mass and fat-free mass were calculated using Brozek's equation (2). Hydrostatic weighing and residual volume were measured in three trials and the mean was used as the final value.Two-factor (3 days, 2 menstrual cycles) repeated measures analysis was used to test the effect of day and cycle on BMR and body weight. (PROC...

Accuracy of resting metabolic rate prediction equations among healthy adults in Trinidad and Tobago

“…The phases of the menstrual cycle are known to affect daily variations in RMR of females (Henry et el., 2003; Plankey et al, 1995). Our analyses did not take into consideration phases of the menstrual cycle in the computation of RMR requirements as many of the younger female participants did not respond to questions on their menstrual cycle or use of contraception.…”