Weight Loss and Fertility: What You Need to Know

Fertility is affected by many factors, and body weight is one of them. Both excess weight and being underweight can disrupt the hormonal balance needed for conception. For people who are trying to conceive, weight management can be an important — and sometimes overlooked — part of fertility care.

How does excess weight affect female fertility?

Insulin resistance — common in people with obesity — raises insulin levels, which in turn raises androgen levels and disrupts ovulation. Polycystic ovary syndrome (PCOS), which is strongly linked to excess weight and insulin resistance, is one of the most common causes of female infertility in the UK. Excess weight is also associated with irregular menstrual cycles, reduced response to fertility treatment, and higher rates of miscarriage.

How does excess weight affect male fertility?

Excess weight in men is associated with reduced testosterone levels, impaired sperm quality, and erectile dysfunction. Visceral fat converts testosterone to oestrogen, further disrupting the hormonal balance needed for healthy sperm production.

What does weight loss do?

Even modest weight loss — 5–10% of body weight — can restore regular ovulation in women with PCOS, improve sperm quality in men, and increase the chances of natural conception. For people undergoing IVF, weight loss before treatment is associated with better outcomes.

Important note

Some treatments used in weight management are not suitable during pregnancy or when actively trying to conceive. A doctor-led assessment will take your fertility goals into account when recommending a management plan.

At Weight Loss Wales, we take a careful, medically supervised approach. Find out more about our programme.