From body mass index to body composition in female infertility.

Obesity - a global epidemic that the World Obesity Federation expects will affect one in five women by 2030 - is an important factor influencing reproductive health. Its impact extends beyond subfertility, encompassing menstrual irregularities, oligo-anovulation, early pregnancy loss, and complications during pregnancy and delivery. The interplay between excess adiposity, metabolic health and reproductive function is complex, as adipose tissue secretes several adipokines, such as adiponectin and leptin, targeting reproductive and endocrine tissues. However, investigating the role of obesity on fertility and choosing how to define and quantify obesity remains a major challenge. Traditional reliance on body mass index (BMI) may oversimplify this relationship, as individuals with similar BMI can exhibit differing levels of metabolic health and fertility outcomes depending on their body composition and fat distribution. This narrative review examines the relationship between body composition, adiposity and abnormal body weight in reproductive health outcomes, with a focus on fertility and treatment success in women. The analysis evaluates the impact of body composition on fertility treatments, particularly IVF, and discusses implications for clinical practice. By synthesizing current evidence, this review aims to inform future research and guide the development of personalized clinical strategies in reproductive medicine.