Compared with women belonging to the “Normal-stable” trajectory, women in the “Normal-overweight” and “Normal-obesity” trajectories had increased risk of ER/PR-positive breast cancer, with respective HRs of 1.09 (95% CI 1.01–1.16) and 1.19 (95% CI 1.08–1.31). This evidence concerns the gene ESR1 and obesity due to melanocortin 4 receptor deficiency.