Body Mass Index and Metabolic Phenotypes in Breast Cancer Risk: A Meta-Analysis and Systematic Review

Introduction: Numerous studies have established that obesity, often assessed through body mass index (BMI), is one of the most significant risk factors for the development of breast cancer (BC). However, not all individuals with obesity have the same risk of developing BC and vice versa. Objective: To determine the association between metabolic states and the risk of BC. Materials: AS systematic review (SR) with a meta-analysis of cohort studies was conducted. The search was performed in four databases: PubMed/Medline, SCOPUS, Web of Science, and EMBASE. Metabolic states were classified as Metabolically Healthy Normal Weight (MHNW), Metabolically Unhealthy Normal Weight (MUNW), Metabolically Healthy Obesity (MHO), and Metabolically Unhealthy Obesity (MUO). Association measures were presented as hazard ratios (HR) with their 95% confidence intervals (CI95%). Results: A total of four studies were evaluated. The meta-analysis found a statistically significant association between the development of BC and the MHO state (HR: 1.14; CI95% 1.02, 1.28) and MUO state (HR: 1.37; CI95% 1.16, 1.62) compared to individuals with MHNW. No association was found with the MUNW state. Conclusions: The findings suggest that obesity, as determined by BMI, is significantly associated with an increased risk of BC, regardless of metabolic state. Additionally, metabolically unhealthy states, especially in obese individuals, appear to increase the risk of BC. Proposed mechanisms include systemic inflammation, metabolic dysfunction, and altered hormone production. These results have important public health implications, emphasizing the need for prevention strategies focused on obesity management and awareness of its associated BC risks.