Assessment of the physical activity level with two questions: validation with doubly labeled water.

Objective:To validate a two-question questionnaire on physical activity with the doubly labeled water (DLW) method.Design:Cross-sectional study.Subjects:Nine volunteers, age 33-75 years, with a mean body mass index (BMI) (kg m(-2)) of 27.4.Measurements:A questionnaire with one question on physical activity at work and one question on physical activity during leisure time. The answers were converted into a PAL (physical activity level=energy expenditure/basal metabolic rate) value, which was validated with the DLW method.Results:The mean values (s.d.) of PAL for the questionnaire and DLW measurements were 1.7 (0.1) and 1.7 (0.1), respectively, with a mean difference of 0.004 (0.172).Conclusions:The results were promising to the extent that they could be used in large-scale epidemiological studies.International Journal of Obesity advance online publication, 8 April 2008; doi:10.1038/ijo.2008.42.