Variations in percentage of body fat within different BMI groups in young, middle-aged and old women.

Objectives: The objective of the present study was to characterize age-dependent variations in percentage of body fat within different body mass index (BMI) classes in healthy Danish women.

Design: Cross-sectional analysis.

Settings: The study was done at the Center for Clinical and Basic Research, Ballerup, Denmark.

Subjects: Four hundred and four healthy women aged 18-75 years were included in the present study.

Measurements: Fat tissue mass was estimated using dual-energy X-ray absorptiometry. Menopausal status and physical characteristics were also registered.

Results: Mean values of percentage of body fat calculated in the normal and overweight BMI groups were higher in middle-aged and old women compared with young women. No significant differences were seen in the underweight and obese BMI groups. The cut-off levels between normal and overweight and between overweight and obesity were 35-43% and 40-50%, respectively.

Conclusion: The percentage of body fat is dependent on both age and menopausal status within each of the following BMI classes: from 20 to 25 and from 25 to 30, further emphasizing that BMI has limitations when used generally as an indicator of body fatness, and argues for defining BMI cut-off values age-specifically.