Background and purpose: Aging is associated with changes in body composition which could lead to malnutrition and disability in elderly people. Physical activity is one of the most important factors that can affect changes in body composition in this population. The purpose of this study was to investigate body composition in elderly and its relationship with pattern of objectively measured physical activity.

Materials and methods: This cross-sectional study was conducted in 368 elderly in Tehran, 2014. Body composition was measured by Bioelectrical Impedance Analysis, and the ActiGraph was used to assess physical activity patterns.

Results: Among the participants 41% were overweight and 19.3% were obese. Abdominal obesity (associated with waist circumference) was seen in 62.22%. The prevalence of obesity and abdominal obesity were higher in women (P<0.001). Fat mass index was high in 59.4% (FMI for men: 5.2-8.2, for women: 8.2-11.7), and very high in 18.8% (FMI for men: ≥ 8.3, for women: ≥11.8). Body fat percentage had direct significant correlation with age (P<0.001), while BMI and waist circumference were found to have significant inverse association with age (P<0.001). The level of physical activity had a significant negative correlation with the percentage of body fat (P<0.001), body fat mass index (P=0.004) and BMI (P=0.03).

Conclusion: Body fat percentage and prevalence of overweight and obesity was high in elderly. The significant association between physical activity and BMI, waist circumference and body fat percentage calls for more attention to adequate levels of physical activity in elderly.