Physical activity in the severely obese : Studies on measurement and promotion

Sammanfattning: Background : The amount and quality of evidence on how to effectively promote physical activity (PA) is low compared to what is known about the health effects of regular PA, especially in obese individuals. Aim : To evaluate the role of social support to promote walking in severely obese outpatients. Methods : The main hypothesis (increased social support promotes walking) was tested through a randomised, 2-armed, prospective (18 weeks) intervention study in 42 severely obese outpatients (study III). Three preparative studies were carried out. Study I was a cross-sectional comparison of PA in severely obese outpatients and a normal weight population. Study II evaluated the digiwalker SW-701 pedometer against the more versatile and sensitive MTI 7164 (formerly CSA) accelerometer. Study IV evaluated the Tanita BC-418 bioelectrical impedance monitor for estimating body composition against dual x-ray absorptiometry (DXA). Results : Study I found a clear inverse association between PA and BMI that was dependent on obesity status (strong correlation in the obese between PA and BMI, and weak or non-existent correlation in non-obese). Study II showed that the digiwalker pedometer was of sufficient quality to confidently detect changes in walking in the intervention study (study III). The Tanita BC-418 bioelectrical impedance monitor correlated well with DXA estimates of fatness, but underestimated both total and trunkal fatness (study IV). In the intervention study (study III) the group allocated to a more intensive support programme recorded 1794 more steps/d than the group allocated to standard support (P<0.01). Conclusions : Accelerometer data identified the need to promote PA in the severely obese. Pedometers were deemed sufficiently accurate to detect changes in walking. Finally, the intervention study provided support for the concept that social support promotes walking in the severely obese.