BMI: Why Your Weight "Speaks" to Your Ovaries

Body weight is one of the most crucial roles in your chances of conceiving, in pregnancy outcomes, and in having a healthy baby. But how can very high or very low body weight affect your ovarian health and overall fertility?

What is the Body Mass Index (BMI)?

The Body Mass Index (BMI) is a tool used to assess body weight in relation to height. It is calculated by dividing weight (in kilograms) by the square of height (in meters):

BMI = Weight (kg) ÷ Height² (m²)

BMI is categorized as follows:

• Underweight: < 18.5 kg/m²
• Normal weight: 18.5–24.9 kg/m²
• Overweight: 25–29.9 kg/m²
• Obese: ≥ 30 kg/m²

How can your weight affect your ovarian health?

Both high and low body weight can disrupt the menstrual cycle, interfering with hormone production and ovulation. Excess body fat is associated with an overactive fatty tissue that functions as an active endocrine gland. Fat cells produce large quantities of estrogens, which disrupt the secretion of FSH (follicle-stimulating hormone) and LH (luteinizing hormone). The result is irregular menstrual cycles or even a complete absence of ovulation. At the same time, the accumulation of fatty tissue raises insulin levels and inflammatory markers in the blood, two factors that negatively affect egg quality and the environment in which eggs develop.

Very low body weight (BMI < 18.5) is equally harmful. When body fat drops below a critical threshold, the body reduces estrogen production, the menstrual cycle becomes disrupted, and in many cases the period disappears entirely, a condition known as amenorrhoea.

Cycle irregularities can appear even in women who are not visibly underweight, but who follow very low-calorie diets, exercise excessively, or lose weight rapidly. In all of these cases, the mechanism is the same: the body perceives itself as under stress and in a state of energy deficit. The brain "decides" that now is not the right time for a pregnancy and halts ovulation as a protective response.

Practical Steps for Successful Outcomes

The BMI can change, and this can provoke a real difference. Reaching a healthy weight improves fertility and assisted reproduction techniques’ outcomes, even with modest changes. Losing 5–10% of body weight in women with a high BMI, or moderate weight gain in underweight women, improves hormones, ovarian health, and ovulation, and lowers pregnancy risks.

The goal is not the perfect diet or an ideal number on the scales. It is the adoption of small but sustainable changes in everyday life, changes that fit your lifestyle and you can maintain in the long term. Improving your nutrition, developing a healthier relationship with food, incorporating moderate exercise, getting adequate sleep, and managing stress are the foundation of fertility.

Our team is by your side at every step of this journey. We are here to help you understand where you stand today, to design a personalized plan together, and to support you on the path to motherhood. Schedule your free medical consultation today and make the first step.