Objective: To measure body composition and analyse the relation to muscle strength, physical activity and functional ability in healthy, old subjects, and to relate the results to an optimal BMI level for the elderly.
Setting: Subjects aged 80 years living at home from the 1914-population in Glostrup, Denmark.
Subjects and method: 121 men and 113 women had their height and weight measured. Body fat mass and fat-free mass were assessed by bioelectrical impedance. Muscle strength was measured as handgrip, elbow flexion, knee extension, body flexion and body extension. Physical activity was self reported and functional ability was assessed by the Physical Performance Test (PPT) and self reported mobility including information about tiredness and help.
Results: After dividing BMI into three groups: BMI < 24, BMI 24-29 and BMI > 29 no relationship was seen between a BMI interval of 24-29 kg/m2, and physical activity and functional ability. BMI was related to body fat mass, and FFM was related to muscle strength. Muscle strength was related to mobility and PPT. Mobility and PPT were mutually related and were related to physical activity.
Conclusion: Our cross sectional study did not support newly proposed guidelines for the elderly of an optimal BMI interval of 24-29 kg/m2. We found relations between body composition, muscle strength, physical activity and functional ability.