According to a recent meta-analysis, obesity had a negative impact on disease-free survival (DFS) and overall survival (OS) for all breast cancer subtypes: the hazard ratios (HR) regarding DFS were 1.26 (95% CI 1.13-1.41) for hormone receptor positive/HER2 negative tumors (HR+HER2-), 1.16 (95% CI 1.06-1.26) for HER2+ cancers, and 1.17 (95% CI 1.06-1.29) for TNBC, whereas the respective values regarding OS were 1.39 (95% CI 1.20-1.62) for HR+HER2- tumors, 1.18 (1.05-1.33) for HER2+ tumors, and 1.32 (95% CI 1.13-1.53) for TNBC 29. Here, ERBB2 is linked to obesity due to melanocortin 4 receptor deficiency.