Increased body fatness does not improve bone health in middle-aged women and may be detrimental, emphasising the importance of maintaining lean body mass from middle age.
A poster presented by Dr Kun Zhu, from Sir Charles Gairdner Hospital in Perth, and colleagues described a study in more than 3,000 women and men aged from 51 to 69 participating in the Busselton Healthy Ageing Study.
DXA scans were used to assess bone mineral density in the whole body, lumbar spine, total hip and femoral neck, and BMD was correlated with measurements of body mass index and fat mass index (FMI, fat mass/height2).
“FMI has been suggested as a more accurate measure of fatness than BMI as it is not affected by other body components such as lean mass,” Dr Zhu said.
“However, data regarding the relationships between FMI and BMD are limited.”
The Busselton volunteers were classified as being underweight/fat deficit, normal, overweight/excess fat, obese and severely obese using standard BMI and FMI categories.
BMI and FMI categories were concordant in about 77% of women and 71% of men. There were 10% of women who were in a lower FMI than BMI category (low body fat for BMI), and 13% in a higher category (high body fat for BMI). For males, the corresponding figures were 16% and 13%.
Women with higher body fat for BMI had significantly lower BMD at the femoral neck, total hip and total body compared to those with concordant FMI or BMI or low body fat for BMI.
The associations persisted after accounting for age, smoking, alcohol intake and physical activity.
In men there were no significant associations between measures of fatness and BMD.