C-reactive protein and physical activity lents (METs) of physical activity and several terti- ary factors, such as adiposity and glycaemic status, is not well-understood. Results of some studies showed that the impact of physical activity is me- diated through its weight-lowering effect (15,16). A study reported that the circulating levels of CRP can be markedly suppressed, independent of total adiposity or fat mass, by intense regular physical exercise (17). The present study was carried out to examine the association among different intensities of physical activity (moderate and severe), total physical activi- ty (using METs for the intensity of activities), dura- tion of sedentary behaviours, and the serum CRP levels after adjustment for glycaemic status and markers of adiposity, including waist-circumference and body mass index (BMI) in a large population- based sample of Iranian adults. Physical activity was defined by an international standard question- naire, named global physical activity questionnaire (GPAQ). MATERIALS AND METHODS Participants The study was based on data collected in the third national surveillance of risk factors of non-com- municable diseases (SuRFNCD-2007). Details of the survey were reported elsewhere (18). In brief, a cluster-sampling scheme was applied to randomly select a representative sample of Iranian adults aged 25-64 years. The number of clusters selected from each province was proportional to the urban/rural size of that province. Trained healthcare profes- sionals conducted household interviews and physi- cal examinations. All interviews were conducted in Persian. Data were recorded in standardized sets of questionnaire. Blood sampling was done within a few days of the interview. The survey received ethical approval from the Cent- er for Disease Control of Iran, and written informed consent was obtained from all the participants. Assessment of physical activity The second version of the GPAQ was used in the survey (19). This questionnaire, developed by the World Health Organization (WHO), contains 16 questions about physical activity in a typical week and assesses physical activity in three domains: work, transportation, and recreational activities. The evaluation of physical activity in these do- mains is one of the factors that make the GPAQ dis- tinct from other sets of questionnaire, such as the less-sophisticated, short version of the internation- al physical activity questionnaire (IPAQ) (http:// Volume 30 | Number 1 | March 2012 Esteghamati A et al. www.ipaq.ki.se). It also determines the intensity of activity (i.e. vigorous or moderate) in each domain and the time spent on sedentary behaviours, such as watching TV. Sedentary behaviours were defined as activities, such as sitting at a desk, travelling in car/bus/train, reading, working with computer, and watching television. To measure energy expenditure, the concept of METs was used (19). MET is the ratio of a person’s working metabolic rate and the resting metabolic rate (19). One MET is defined as the energy cost of sitting quietly and is equivalent to a caloric con- sumption of 1 kcal/kg/hour. It is estimated that a person’s caloric consumption is four times high when moderately active and eight times high when vigorously active. Therefore, to calculate a person’s overall energy expenditure, four METs are assigned to the time spent on moderate activities, and eight METs are assigned to the time spent on vigorous activities. The total physical activity (TPA) score was calculated as the sum of all METs × min- utes for moderate- or vigorous-intensity physical activity performed in work, commuting, and rec- reation. Based on the GPAQ analysis framework (19), our participants were classified into three groups of high, moderate and low physical activity catego- ries. More details on these definitions were reported elsewhere (20,21). Physical examination and biochemical measurements Weight and height were measured in light clothing and without shoes. A portable calibrated electronic weighing scale (Omron Corp., Tokyo, Japan) and portable measuring inflexible bars (Seca, Hamburg, Germany) were used for this purpose. A constant tension tape (Seca, Hamburg, Germany) was used for measuring waist-circumference at the end of a normal expiration, with arms relaxed at the sides, at the midpoint between the lower margin of the lowest rib and the highest point of the hip on the mid-axillary line. The BMI (kg/m2) was calculated according to the Quetelet formula. Five mL of ve- nous blood was taken in sitting position, centri- fuged, and transferred under cold-chain condition to the laboratory. Quantitative CRP concentrations in serum were measured in the endocrine labora- tory of the Vali-Asr Hospital (Tehran University of Medical Sciences) using the quantitative CRP kit (Parsazmoon, Karaj, Iran), with an intra-assay coef- ficient of variation of 2.6%. Diabetes was diagnosed following the criteria of the American Diabetes As- sociation as described in our previous report (22). 67