Weight and Fertility: How BMI Affects Your Ability to Conceive

The Link Between Weight and Fertility

Maintaining a healthy weight plays a crucial role in fertility for both women and men. Being underweight or overweight can affect ovulation, hormone production, and sperm quality, reducing the chances of conception.

Up to 30% of infertility cases are influenced by weight-related factors. The good news? Losing as little as 5-10% of body weight can significantly improve fertility outcomes and increase the chances of a healthy pregnancy.

How BMI Affects Female Fertility

1. Overweight & Obesity (BMI > 25)

• Irregular ovulation (anovulation) – Excess body fat leads to higher oestrogen levels, which can disrupt ovulation cycles.
• Polycystic Ovary Syndrome (PCOS) – Obesity increases insulin resistance, worsening PCOS symptoms and reducing egg quality.
• Increased miscarriage risk – Studies show a higher risk of pregnancy loss in women with a BMI over 30.
• Lower IVF success rates – Obesity can reduce implantation rates in assisted reproduction treatments.

Did you know? Women with a BMI over 30 take twice as long to conceive compared to those in a healthy weight range 

2. Underweight (BMI < 18.5)

• Low oestrogen levels – Not enough body fat can lead to irregular periods or missed ovulation.
• Higher risk of miscarriage – Women with a very low BMI may struggle to sustain a pregnancy due to poor endometrial lining development.
• Reduced egg quality – Nutritional deficiencies can impact egg maturation and implantation success.

How Weight Affects Male Fertility

Men’s fertility is also impacted by weight, affecting sperm quality, testosterone levels, and overall reproductive health.

1. Obesity & Male Fertility

• Low sperm count & motility – Excess fat can lead to hormonal imbalances, lowering testosterone and sperm production.
• Increased DNA fragmentation – Obesity is linked to higher sperm DNA damage, reducing fertilisation success.
• Erectile dysfunction (ED) – Overweight men are at greater risk of vascular issues that impact sexual performance.

2. Being Underweight & Male Fertility

• Lower testosterone levels – Not enough body fat can reduce sperm production.
• Poor sperm morphology – Nutritional deficiencies can lead to abnormal sperm shape, reducing fertility.

Fact: Studies show men with a BMI over 30 have a 30% higher risk of infertility.

Weight & Fertility: BMI vs. Conception Rates

Conception Rates by BMI Category

• Healthy BMI (18.5-24.9): ~80% conceive within 12 months
• Overweight BMI (25-29.9): ~65% conceive within 12 months
• Obese BMI (>30): ~50% conceive within 12 months

Healthy Weight Management for Fertility

1. Balanced Diet for Fertility

• Eat whole foods, lean protein, and healthy fats to regulate hormones.
• Increase iron, folate, and omega-3s to support egg & sperm health.
• Reduce processed foods, sugar, and trans fats, which can disrupt fertility hormones.

2. Exercise & Lifestyle Adjustments

• Moderate exercise (30 mins/day) can improve ovulation & sperm health.
• Avoid excessive exercise – Too much high-intensity training can affect menstrual cycles.

3. Medical Support for Weight & Fertility

• If struggling with weight-related fertility issues, consider hormonal assessments & specialist guidance.
• Medications can help manage weight & insulin resistance in PCOS.
• Fertility treatments (IVF, ovulation induction) may be an option for overweight or underweight individuals.

Take Control of Your Fertility

Maintaining a healthy weight is one of the most effective ways to boost fertility naturally. If you’re planning a pregnancy and concerned about weight and fertility, Dr. Basu can provide expert guidance to optimise your reproductive health.