Comparison of physical activity level between overweight/obese and normal weight individuals: A systematic review

Context: The relationship between activity levels and body fat is unclear, despite large number of studies. This issue is clouded by the wide methods used to measure body fatness and activity levels. Objective: To review published prospective observational studies evaluating the associations between body fatness and physical activity, with emphasis on methodological issues. Data sources: Published English-Language studies were located from PubMed and bibliographies of primary studies. Data extraction: Sample size, population studied, measures of activity and body fatness, statistic approach, and main findings were extracted, summarized, and key methodological issues highlighted. Results: In total, 58 studies were identified and reviewed. Results were mixed, with most studies showing an inverse association of physical activity with fatness. The effects identified were generally of small magnitude. Imprecise measurement of activity and small sample sizes likely weakens the observed relationships. On balance, combinations of methods of activity measures tend to produce a better result. Consistently documented high effect sizes were found for all studies that used 18-Oxygen for assessing body fatness and doubly labelled water for activity measure. Conclusions: This review suggests that there is small to moderate inverse relationship body fatness and activity. The association is in favour of male and younger subjects. It is important to note, however, that there is a need more research on uniform ways of activity and fatness measures.