Specifically, a 2019 MR analysis found that BMI was inversely associated with the risk of overall breast cancer, and ER+ (luminal A, luminal B and luminal B/HER2 negative) and ER− (HER2+ and triple negative) sub-types, using a similar dataset—although with less cancer cases—to the BCAC study [31]. The gene discussed is ERBB2; the disease is cancer.