Perimenopause and metabolic vulnerability: hormones, body composition and lifestyle changes.

Perimenopause is a transitional phase characterized by substantial hormonal fluctuations, particularly declining estradiol levels, accompanied by age-related metabolic changes. Increasing evidence suggests that this period constitutes a critical window of metabolic vulnerability, marked by adverse alterations in body composition, energy metabolism and cardiometabolic health. Notably, these changes may develop even without significant increases in body weight, potentially delaying their recognition in clinical settings. A narrative review was conducted using the PubMed/MEDLINE, Scopus, Web of Science and SciELO databases. Studies involving perimenopausal women, plus relevant animal models, were included. Search terms covered estrogen deficiency, body composition, metabolism, insulin resistance, inflammation, physical activity and nutrition. Fifty-six studies published between 2000 and 2026 were analyzed. Evidence shows that perimenopause is characterized by increased visceral fat, loss of lean mass, reduced fat oxidation and impaired metabolic flexibility, even without major weight changes. Declining estrogen drives adipose redistribution, muscle dysfunction, hepatic insulin resistance and chronic low-grade inflammation. These changes heighten risk for metabolic syndrome, type 2 diabetes and cardiovascular events. Lifestyle interventions, particularly resistance training and Mediterranean diet adherence, demonstrate strong potential to preserve muscle, improve insulin sensitivity and reduce inflammation. In conclusion, perimenopause should be recognized as a pivotal stage for early detection and prevention of metabolic dysfunction. Lifestyle-based interventions during this phase may reduce long-term cardiometabolic risk and improve women's health.