engleski

Variations in metabolism and body composition estimates throughout a day

Background: Values of resting metabolic rate are very important for determining optimal daily caloric intake. Body fat percentage is one of the most important indicators of health. However, there are possibilities for making mistakes in estimating these values. This study aimed to investigate possible variations in metabolism and body composition estimates throughout a day, depending on the time of the day the measurement is conducted. Methods: 20 male adults (age=24.3±3.3 years, height=180.8±19.5 cm, weight=80.3±35.1 kg) completed three resting metabolic rate and body composition tests during one day, in the morning (8 am) after waking up and fasting from food, caffeine and alcohol for 12 hours, in the middle of the day (1 pm) and in the evening (5 pm). All participants followed a self-selected diet throughout the day in addition to fasting 2 hours before the middle of the day and evening measurements. Results: The test results and comparison have shown significant (p≤0.05) differences between morning resting metabolic rate and middle of the day and evening resting metabolic rates. Resting metabolic rate estimations (8670±1581 kJ) were lowest in the morning and more closely approximated to the basal metabolic rate estimation (8660±774 kJ) of the bioelectrical impedance analysis. Results obtained using skinfold measurements to asses body composition showed no statistically significant difference (p>0.05) depending on time of measurement. The only significant differences in body fat estimations over the course of the day, though small (~0.8%) were from bioelectrical impedance analysis. Conclusion: Morning assessments were lowest regardless of the measurement, and body fat estimates via skinfold calliper do not appear to be as affected when measured multiple times within the same day as do body fat estimates via bioelectrical impedance analysis.

resting metabolic rate ; skinfold ; bioelectrical impendance analysis ; Tanita

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