Normal weight obesity and the risk of liver cancer in 0.3 million Chinese adults: a prospective multicenter cohort study.

BACKGROUND

Obesity has been found to be an independent risk factor for liver cancer. However, whether normal-weight obesity (NWO), defined as a normal body mass index (BMI) but high body fat content, is associated with an increased risk of this cancer remains unknown. We performed a prospective multicenter cohort study to examine the potential association of NWO with the risk of liver cancer in a nationally representative Chinese population.

MATERIALS AND

METHODS

A total of 319 781 Chinese adults with a normal BMI (18.5-24.9 kg/m 2 ) were included and followed up through 31 December 2018. Participants in the highest sex-specific tertile of body fat percentage were classified into NWO group. Cox regression was used to calculate hazard ratio for liver cancer incidence. Subgroup analyses were conducted to identify the potential effect modifiers.

RESULTS

During an average follow-up of 11.75 years, 1495 liver cancer cases occurred. In the fully adjusted model, NWO was found to be associated with an elevated risk of liver cancer (hazard ratio 1.22, 95% confidence interval 1.07-1.39), which remained in both propensity-score-adjusted and -matched analyses. Subgroup analysis revealed a stronger positive association in HBsAg-negative participants than in those with HBsAg positivity ( Pinteraction  = 0.008). Body fat percentage was found to be positively associated with the risk of liver cancer in a nonlinear dose-response manner ( Pnonlinearity  < 0.001). No significant joint association of central obesity and NWO with the risk of liver cancer was found ( Padditive interaction  = 0.298). Similar results were obtained when the above analyses were performed in men and women separately.

CONCLUSIONS

NWO confers an increased risk of liver cancer in this Chinese population. Our findings suggest that body fat loss may be beneficial in reducing liver cancer risk in individuals with a normal BMI, and highlight that the traditional BMI categorization may be inadequate in risk stratification of this cancer.