High obesity rates and mismatch between BMI and waist circumference in older adults: sex-specific patterns from the NutriCare study

Abstract Purpose Anthropometric thresholds used to define obesity and central obesity are largely derived from younger populations, although aging is accompanied by marked alterations in body composition and fat distribution. We investigated age- and sex-specific patterns of body mass index (BMI) and waist circumference (WC) in very old adults and evaluated how these measures relate to glucose metabolism. Methods In this cross-sectional analysis of the NutriCare study, 387 relatively independent residents aged 65–101 years from 20 nursing homes were assessed. Standardized anthropometry was performed, and body composition was estimated using bioimpedance spectroscopy. Obesity was defined using WHO BMI criteria, and central obesity using established WC cut-offs for Caucasian populations. Associations with fasting glucose and documented type 2 diabetes (T2D) were examined separately in men and women. Results Participants (220 women, 167 men; mean age 81 ± 8 years) had a high burden of excess adiposity, with central obesity more frequent than BMI-defined obesity. Advancing age was accompanied by reductions in BMI in both sexes, with declining fat mass in men and decreasing WC in women. The correlation between BMI and WC attenuated with increasing age. Both adiposity indicators were associated with higher fasting glucose concentrations, while a higher prevalence of documented T2D was observed only among participants with BMI-defined obesity. Conclusion In very old adults, central obesity is common, yet the relationship between BMI, WC, and metabolic risk may differ from patterns observed in younger populations. These exploratory findings suggest that the diminishing agreement between BMI and WC at higher age may indicate that conventional anthropometric thresholds do not fully capture adiposity-related risk in late life. Further research in larger and more diverse cohorts is needed to inform age- and sex-specific approaches to obesity assessment in older adults. Trial registration The study was registered in clinicaltrials.gov (NCT05389618) on 25.05.2022.