Daily energy expenditure of middle-aged Japanese housewives measured by 24-hour heart rate and diary

Measurements of daily energy expenditure were made in 20 middle-aged Japanese housewives by 24-hour heart rate monitoring. The values were compared with the estimates derived from the diaries being simultaneously recorded by the subjects on the nature and duration of activities during the 24-hours. The mean of the energy expenditure derived from the 24-hour heart rate was 1476 kcal, while the mean of the estimates from the diaries was 2007 kcal. The assessed error in the heart rate method was about 10% over-estimation. As the energy expenditure derived from the diary method was 36% greater than that of the heart rate method, the error involved in the diary method was much greater than that in the heart rate method. The difference in the estimation between the two methods resulted from two causes. The first is in the resting metabolic rate which accounts for a 15% greater estimate; 0.84 kcal/min (31.0 kcal/kg fat-free mass/24 hour) determined by oxygen consumption, and 0.96 kcal/min (35.6 kcal/kg fat-free mass/24 hour) calculated from the Japanese standard basal metabolic rate. The second is a suggested limitation of the diary method that the recorded activities may not appropriately reflect dominant activities, which accounts for the rest of 21% greater estimate. If the daily energy expenditure is estimated on the basis of the diary method without knowing the extent of error involved, an erroneous conclusion would be drawn.