Underweight

Being underweight means that you have a Body Mass Index (BMI) under 18.5. BMI is your weight in kilograms divided by your height in meters squared. If you are underweight, it has negative effects on your general health, in addition to your hormones and fertility.

This article has been verified by a medical professional

Impact of being underweight on fertility

Having a low weight can lead to hormonal imbalances. The body may stop producing estrogen altogether, which messes with your menstrual cycle. Your period may become irregular or stop completely (having no periods at all is called amenorrhea). Not having a period can signal that you’re not ovulating. Without ovulation, it’s not possible to get pregnant.

Besides the trouble conceiving, a low BMI during pregnancy increases the risk of complications including miscarriage, preterm birth, having a baby with a low birth weight and gastroschisis (a condition where the baby’s stomach doesn’t develop as it should).

Potential causes of being underweight

There are a few possible reasons for being underweight, namely:

• Not eating enough, for instance because of an eating disorder like anorexia or loss of appetite due to stress
• Overactive thyroid (hyperthyroidism), which also reduces fertility
• Exercising too much
• Digestive problems including celiac or Crohn’s disease
• Diabetes

Some women are genetically predisposed to having a low body weight.

Symptoms of being underweight

When you weigh too little, it can have a few adverse health effects, such as:

• Weakened immune system, making you more vulnerable to catch colds and other illnesses
• Fatigue
• Fragile bones

Treatment to improve fertility

Talk to your doctor to get to the bottom of what’s causing your low weight and decide on the best course of action. In general, your chances of conceiving will be much higher if you can get your BMI to between 20 and 25.

If the reason you are underweight is that you are eating too little, switching to a balanced diet can improve your health and fertility. Don’t turn to high-calorie, sugary foods with lots of saturated fats like chocolate, cakes and sugary drinks to increase your weight, as these raise body fat as well as your risk for high cholesterol.

To get to a healthy weight, here are some guidelines to follow:

• Eat 5 portions of fruits and veggies each day
• Have meals with starchy carbs, such as potatoes, bread (preferably wholegrain), rice, or pasta
• Get more protein into your diet by eating beans, fish, eggs, and meat
• Eat healthy snacks with high amounts of unsaturated fats, like unsalted nuts
• Drink 8 glasses of water per day, but don’t drink too much right before eating as this can make you feel full

In case you notice that you feel anxious about eating or that low self-esteem is impacting your relationship with food, an eating disorder may be what’s causing you to be underweight. Eating disorders are common among young women, and you’re definitely not alone. Speaking to a mental health professional can help you understand why you have negative feelings around food and your body and develop some coping strategies to improve your overall well-being. A dietitian can also assist you with meal planning to get you to a healthy weight.

But having a low weight isn’t always related to how much food you eat. If you notice symptoms such as sensitivity to heat, sleeping problems, hair loss and trembling hands, a thyroid disorder may be the reason you are underweight. If that’s true, medication can help you balance your thyroid hormones and also greatly improve your fertility.

This article has been verified by a medical professional

• Underweight and fertility when planning a pregnancy. Tommy’s. Accessed 15 September 2022.
• Underweight adults. NHS. Accessed 15 September 2022.
• Does Being Underweight Affect Fertility. LA IVF. Accessed 15 September 2022.