Abstract
Exercise reduces the risk of breast cancer development and improves survival in breast cancer patients. However, the underlying mechanisms of this protective effect remain to be fully elucidated. It is unclear whether exercise can attenuate or modify the pro-tumour effects of obesity and related conditions, such as hyperlipidaemia. This review summarises how hyperlipidaemia and exercise contribute to or reduce breast cancer risk and progression, respectively, and highlights the possible mechanisms behind each. In particular, the effects of exercise and hyperlipidaemia on the immune microenvironment of tumours is analysed. The potential value of commonly investigated circulating factors as exercise-modulated, prognostic biomarkers is also discussed. We propose that exercise may alleviate some of the pro-tumorigenic effects of hyperlipidaemia through the reduction of blood lipid levels and modulation of cytokine release to induce beneficial changes in the tumour microenvironment.