Nonlinear association between body fat percent and type 2 diabetes risk in Japanese adults: a retrospective cohort study.

BACKGROUND

Type 2 diabetes (T2D) has emerged as a major global public health challenge, with dyslipidemia playing a pivotal role in its pathogenesis. Body fat percentage (BFP), a direct measure of adiposity, surpasses body mass index (BMI) in identifying metabolic risk; however, its prospective association with incident T2D remains unclear.

OBJECTIVE

To systematically investigate the association between BFP and the risk of incident T2D and to identify potential nonlinear thresholds.

METHODS

A large-scale retrospective cohort study was conducted involving 15,464 Japanese adults with a mean follow-up of 6.05 years. Cox proportional hazards regression models were employed to estimate hazard ratios (HRs), and restricted cubic spline analyses were performed to assess nonlinear relationships.

RESULTS

BFP was identified as an independent risk factor for T2D. After comprehensive adjustment for confounders, each 1% increase in BFP corresponded to a 6% increase in T2D risk (HR = 1.06, 95% CI: 1.04-1.09). Crucially, restricted cubic spline analysis revealed a significant nonlinear "hockey-stick" pattern, identifying an inflection point at 21.65%. Below this threshold, the risk rose sharply with increasing BFP (HR = 1.18, 95% CI: 1.03-1.36); above it, the upward trend plateaued. This association remained robust in subgroups with normal waist circumference and absence of fatty liver disease, underscoring BFP's unique utility in detecting normal-weight obesity.

CONCLUSION

BFP serves as a crucial predictor of T2D. Maintaining BFP below 21.65% may represent a novel target for personalized diabetes prevention strategies.