Validating measures of free-living physical activity in overweight and obese subjects using an accelerometer

• Published in: International Journal of Obesity Vol. 38; no. 7; pp. 1011 - 1014
• Main Authors: Valenti, G, Camps, S G J A, Verhoef, S P M, Bonomi, A G, Westerterp, K R
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2014; Nature Publishing Group
• Subjects: 692/699/2743/393; 692/700; Accelerometers; Accelerometry; Adult; Bias; Biological and medical sciences; Body mass index; Body size; Body Weight; Confidence intervals; Energy; Energy expenditure; Energy Metabolism; Epidemiology; Estimates; Exercise; Female; Health aspects; Health Promotion and Disease Prevention; Humans; Internal Medicine; Living conditions; Male; Measurement; Medical sciences; Medicine; Medicine & Public Health; Men; Metabolic Diseases; Metabolic rate; Metabolism; Monitoring, Ambulatory - instrumentation; Monitoring, Ambulatory - methods; Motor Activity; Obesity; original-article; Overweight; Overweight persons; Physical activity; Physiological aspects; Prediction models; Public Health; Reproducibility of Results; Respiration; Weight control; Netherlands; accelerometry; validation; physical activity; doubly-labeled water; Water; Physical exercise; Human; Obesity; Nutrition; Body weight; Nutrition disorder; Label; Metabolic diseases; Corporal biometry; Overweight; Test validation; Accelerometer; Accelerometry; Nutritional status
• ISSN: 0307-0565; 1476-5497; 1476-5497
• DOI: 10.1038/ijo.2013.195

Background: Free-living physical activity can be assessed with an accelerometer to estimate energy expenditure but its validity in overweight and obese subjects remains unknown. Objective: Here, we validated published prediction equations derived in a lean population with the Tracmor D accelerometer (DirectLife, Philips Consumer Lifestyle) in a population of overweight and obese. We also explored possible improvements of new equations specifically developed in overweight and obese subjects. Design: Subjects were 11 men and 25 women (age: 41±7 years; body mass index: 31.0±2.5 kg m −2 ). Physical activity was monitored under free-living conditions with Tracmor D , whereas total energy expenditure was measured simultaneously with doubly-labeled water. Physical activity level (PAL) and activity energy expenditure (AEE) were calculated from total energy expenditure and sleeping metabolic rate. Results: The published prediction equation explained 47% of the variance of the measured PAL ( P <0.001). PAL estimates were unbiased (errors (bias±95% confidence interval): −0.02±0.28). Measured and predicted AEE/body weight were highly correlated ( r 2 =58%, P <0.001); however, the prediction model showed a significant bias of 8 kJ kg −1 per day or 17.4% of the average AEE/body weight. The new prediction equation of AEE/body weight developed in the obese group showed no bias. Conclusions: In conclusion, equations derived with the Tracmor D allow valid assessment of PAL and AEE/body weight in overweight and obese subjects. There is evidence that estimates of AEE/body weight could be affected by gender. Equations specifically developed in overweight and obese can improve the accuracy of predictions of AEE/body weight.