Fertility is a journey full of nuances where weight plays a very important role. Both low weight and excess kilos can influence the ability to conceive and the course of pregnancy. Here we explain in simple terms how weight affects fertility and what actions you can take.
How does low weight affect fertility?
When your BMI is below 18.5 kg/m², the body lacks sufficient energy and the hypothalamic-pituitary-ovarian axis reduces the release of GnRH, estrogen, and progesterone. This can cause irregular cycles (oligomenorrhea) or absence of menstruation (amenorrhea), making ovulation difficult.
Additionally, the lack of key nutrients such as iron, omega-3, vitamins B12 and D can affect oocyte quality and uterine receptivity. If you become pregnant with low weight, the risk of preterm birth and a baby weighing less than 2,500 g increases. Avoid self-medication and always consult a professional.
How does overweight influence fertility?
With a BMI ≥30 kg/m², in women insulin resistance, hyperandrogenism, and ovulatory dysfunction increase, favoring conditions such as PCOS and thyroid problems. During pregnancy, the risk of gestational diabetes, preeclampsia, and obstetric complications rises.
In men, excess fat raises scrotal temperature and converts more testosterone into estrogen, reducing sperm count and quality. Research shows increased sperm DNA fragmentation and morphological alterations.
Weight management strategies to improve fertility
Balanced diet
Include fruits, vegetables, lean proteins, healthy fats (avocado, olive oil), and complex carbohydrates (oats, quinoa). Limit ultra-processed foods and refined sugars. Before supplementing or taking medication, consult a reproductive specialist.
Moderate exercise
Walking 30 minutes a day, swimming, or practicing yoga helps improve insulin sensitivity and cardiovascular health without stressing the reproductive axis. Avoid excessive training that elevates cortisol and affects ovulation.
Specialist support
An assisted reproduction team will offer you a personalized plan based on your history, lab tests, and lifestyle. With metabolic evaluation, nutritional advice, and, if necessary, hormonal treatment, your chances of conceiving are optimized.
When to seek medical help?
If after 6–12 months of dietary and exercise changes you haven’t achieved pregnancy, it’s time to see a specialist. Hormonal studies, ultrasounds, and semen analyses will be performed to identify the cause and define the best protocol (timed intercourse, intrauterine insemination, or IVF). Periodic follow-up allows for treatment adjustments and maximizes success.
Frequently Asked Questions (FAQ)
1. What is the ideal BMI for conception?
A BMI between 18.5 and 24.9 kg/m² offers a stable hormonal environment and increases the chances of pregnancy. But each person is different: age, genetics, and background have an impact, so a personalized evaluation is key.
2. Which nutrients should I prioritize if I’m underweight?
Ensure iron (18 mg/day), omega-3 (EPA and DHA, 200–300 mg/day), vitamin D (600 IU/day), and protein (1.2 g/kg). Legumes, fatty fish, nuts, and fortified dairy will help. Consult a specialized nutritionist.
3. Can exercise be counterproductive?
Moderate exercise (30–60 min, 3–5 days/week) is beneficial. Very high-intensity training or marathons can raise cortisol and disrupt the menstrual cycle. Combine light cardio, strength, and flexibility according to your tolerance and medical recommendations.
4. What treatment options are available if lifestyle changes don’t work?
After 6–12 months without pregnancy, the specialist may suggest timed intercourse, intrauterine insemination, or IVF, depending on your diagnosis. Hormonal tests, ultrasounds, and semen analyses help design the most suitable plan.
Sources Consulted
- American Society for Reproductive Medicine. (2020). Clinical Practice Guidelines on Obesity and Reproductive Health. DOI:10.1097/GRF.0000000000000547
- Centers for Disease Control and Prevention. (2021). Pregnancy and Weight Gain. Retrieved from https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pregnancy-weight-gain.htm
- MedlinePlus. (2023). Infertility. Retrieved from https://medlineplus.gov/infertility.html
- World Health Organization. (2018). WHO Guidelines on Nutritional Interventions for Reproductive Health. Retrieved from https://www.who.int/publications/i/item/9789241550438
We know that the path to parenthood can be challenging. You are not alone: rely on an assisted reproduction specialist to answer your questions and accompany you every step of the way.