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.