Western lifestyle, characterized by reduced physical activity and a diet rich in fat, refined carbohydrates, and animal protein is associated with high prevalence of overweight, metabolic syndrome, insulin resistance, and high plasma levels of several growth factors and sex hormones. Most of these factors are associated with breast cancer risk and, in breast cancer patients, with increased risk of recurrences. Recent trials have proven that such a metabolic and endocrine imbalance can be favorably modified through comprehensive dietary modification, shifting from Western to Mediterranean and macrobiotic diet.