Objective  To investigate the associatiojn of body mass index (BMI) at different stages of life and weight gain in adulthood with obesity-related breast cancer risk biomarkers and to provide evidence for formulating policies concerning the prevention and control of breast cancer.

  Methods  A cross-sectional study was designed based on the follow-up cohort of southwest China community-based breast cancer screening of women. Using sequential sampling, eligible participants were enrolled from the cohort as the subjects of the study. Information on the basic risk factors was collected and the height, weight, and plasma biomarker levels were measured. Multiple linear regression model was applied to analyze the associations of early adulthood BMI (defined as the BMI of the participant at age 20), adulthood BMI (defined as the BMI measured at the time of enrollment), and weight gain in adulthood with the biomarkers. The concentrations of the biomarkers were incorporated in the model after log transformation.

  Results  The average age of the 442 participants was 49 (45, 54) years old, the average early adulthood BMI and adulthood BMI were 21.47 (19.56, 23.11) and 24.10 (22.59, 25.97) kg/m², respectively, and the average weight gain in adulthood was 6.60 (2.00, 11.00) kg. Adulthood BMI was negatively associated with adiponectin level (β=−0.026, 95% CI: −0.045-−0.008, P=0.006), and positively associated with C-reactive protein level (β=0.095, 95% CI: 0.054-0.137, P<0.001) and leptin receptor level (β=0.090, 95% CI: 0.063-0.117, P<0.001). No association was found between adulthood BMI and resistin levels or between adulthood BMI and insulin-like growth factor-binding protein-3 levels. BMI in early adulthood was found to be negatively associated with only insulin-like growth factor-binding protein-3 levels (β=−0.039, 95% CI: −0.068-−0.010, P=0.009). Further analysis of adulthood weight gain after the age of 20 revealed that average annual weight gain in adulthood was negatively associated with adiponectin levels and positively associated with 4 other biomarkers. Furthermore, compared with those of women whose weight remained stable, the adiponectin level of women whose weight gain in adulthood exceeded 5.00 kg was much lower (β=−0.185, 95% CI: −0.320-−0.049, P=0.008), while their insulin-like growth factor-binding protein-3 (β=0.389, 95% CI: 0.183-0.594, P<0.001) and leptin receptor (β=0.245, 95% CI: 0.048-0.442, P=0.015) levels were higher.

  Conclusion  Weight gain in adulthood is strongly associated with the changes in obesity-related breast cancer risk biomarkers. Women should maintain a stable weight throughout adulthood and it is preferred that their weight gain should not exceed 5.00 kg.