When you’re trying to conceive, there’s a lot of advice flying around—what to eat, how often to try, what supplements to take. But one of the biggest, and often overlooked, factors in fertility is something many people struggle with silently: body weight. So, let’s talk honestly and openly—does being underweight or overweight affect fertility? The short answer is yes, but there’s so much more to it than just numbers on a scale.

We’re going to unpack the science behind it, explore how weight impacts hormones, talk about emotional and mental health, and most importantly, look at what you can do if your weight is affecting your ability to conceive. This isn’t about shaming or oversimplifying. It’s about understanding your body better and giving yourself the best possible chance on your fertility journey.

How Does Being Underweight or Overweight Affect Fertility?

This is the million-dollar question, right? And yes—it’s been studied extensively. The link between body weight and fertility is well-established for both women and men. Whether you’re underweight or overweight, your reproductive system can be thrown out of balance.

Let’s break it down. When your body isn’t at a healthy weight (which varies from person to person), your hormone levels may shift in ways that make conception more difficult. Ovulation, menstrual regularity, sperm quality, and overall reproductive function are all closely tied to the body’s endocrine system—and body fat plays a surprisingly large role in hormone regulation.

So yes, the answer to “Does being underweight or overweight affect fertility?” is a clear yes. But understanding how and why makes all the difference.

The Science of Weight and Hormones

Your body fat isn’t just stored energy—it’s actually part of your hormonal orchestra. Adipose tissue (aka body fat) produces estrogen, a key hormone involved in the menstrual cycle. Too much or too little estrogen can interfere with ovulation, making it harder to conceive.

1. In people with too little body fat (often underweight), estrogen production can drop too low, which may result in irregular periods or even complete absence of menstruation (amenorrhea).

       2. In people with too much body fat (overweight or obese), estrogen levels may become too high, which can also disrupt ovulation and lead to hormone-related                 conditions like PCOS (Polycystic Ovary Syndrome).

Both extremes can throw your menstrual cycle out of sync, which makes tracking ovulation tricky—and getting pregnant more challenging.

Being Underweight and Fertility: What You Need to Know

Being underweight often means your body doesn’t have enough fat stores to support regular reproductive functions. This can be due to genetics, high physical activity levels (like athletes), eating disorders, or chronic illness.

Common signs that low body weight is affecting fertility:

1. Irregular or missing periods

2. Feeling constantly fatigued or cold

3. Thinning hair or dry skin

4. Difficulty gaining weight despite eating

When your body senses that it’s in an energy-deficient state, it may shut down non-essential functions like reproduction. That’s a survival mechanism—it’s your body’s way of saying, “Now’s not a good time to have a baby.”

This is one reason why the question “does being underweight or overweight affect fertility?” is such a powerful one—being underweight can lead to a complete halt in ovulation.

But here’s the good news: even small, healthy weight gains can restore hormonal balance and bring back regular periods, especially if the underlying causes (like over-exercising or undereating) are addressed.

Being Overweight and Fertility: What Happens to Your Body?

On the flip side, carrying excess weight can also affect fertility. This is more common than many people realize—and it’s nothing to be ashamed of. About 1 in 3 adults are classified as overweight or obese, and many still go on to conceive successfully. But it may take longer or require additional support.

When body fat increases, so do estrogen levels. Over time, this can lead to:

1. Irregular ovulation or anovulation (no ovulation)

2. Longer or shorter menstrual cycles

3. Increased risk of insulin resistance, which contributes to PCOS

4. Increased inflammation in the body, which can impair reproductive function

And it’s not just female fertility that’s impacted—sperm quality can also take a hit. Studies show that obesity in men is associated with lower sperm count, reduced motility (movement), and higher DNA fragmentation rates.

Again, this isn’t about blame. It’s about awareness. When we ask if being underweight or overweight affects fertility, we have to look at the whole picture—male and female, physical and emotional.

The Mental and Emotional Side of Weight and Fertility

This is such an important piece of the puzzle that doesn’t get talked about enough.

Struggling with weight—on either end of the spectrum—can be incredibly emotional. Add in the stress of trying to conceive, and it can start to feel overwhelming. You may feel frustrated, defeated, or even ashamed. But please hear this: your worth is not defined by your weight, and fertility struggles are not your fault.

When we talk about whether being underweight or overweight affects fertility, we have to also talk about self-compassion, mental health, and support systems. Because managing weight in a healthy way—especially while TTC (trying to conceive)—requires more than just willpower. It requires understanding, patience, and often, professional help.

How Much Weight Is “Too Much” or “Too Little”?

Let’s talk numbers for a second, while keeping in mind that BMI (Body Mass Index) is just one piece of the puzzle and doesn’t tell the full story.

1. A BMI under 18.5 is considered underweight.

2. A BMI between 18.5 and 24.9 is considered normal or healthy.

3. A BMI between 25 and 29.9 is considered overweight.

4. A BMI over 30 is considered obese.

Now, this doesn’t mean that everyone under 18.5 or over 30 will have trouble conceiving. It just means that statistically, fertility challenges become more common outside of the “normal” BMI range.

Even a 5–10% weight change in either direction (gain or loss) can have a big impact on your reproductive health. If you’re asking if being underweight or overweight affects fertility, know that sometimes even small changes can help reset your hormonal balance and improve outcomes.

Lifestyle Changes That Can Help

If you’re wondering how to improve your fertility through healthy weight management, here are some steps that can make a real difference:

1. Focus on Nourishment, Not Restriction

Whether you need to gain or lose weight, extreme diets are not the answer. Focus on whole foods—lean protein, complex carbs, healthy fats, and lots of fruits and vegetables. Aim to fuel your body, not punish it.

2. Find Movement You Enjoy

Exercise should energize you, not exhaust you. If you’re underweight, avoid overtraining. If you’re overweight, aim for gentle, consistent movement like walking, swimming, or yoga. Even 30 minutes a day can help regulate hormones.

3. Work with a Fertility-Savvy Dietitian

A registered dietitian who understands reproductive health can be an incredible ally. They can help you create a plan that supports hormone balance without obsession or deprivation.

4. Manage Stress and Sleep

Chronic stress can worsen hormonal imbalances, and poor sleep disrupts everything from metabolism to mood. Try meditation, journaling, therapy—or simply give yourself permission to rest.

5. Consider Medical Support

If weight is a barrier to conception, you don’t have to go it alone. Your doctor may recommend lab work, hormone testing, or refer you to a reproductive endocrinologist. Sometimes medication or fertility treatments are needed—and that’s okay.

When to Seek Help

If you’ve been trying to conceive for over a year (or six months if you’re over 35), it’s time to talk to a healthcare provider—especially if your periods are irregular or absent, or if you suspect that weight might be a factor.

It’s not admitting defeat. It’s taking a proactive step toward understanding your unique body and getting the support you need.

Real Talk: Every Body Is Different

Here’s something important: not everyone at a low or high weight will have fertility issues. And not everyone in the “ideal” weight range will conceive easily either. Your body is unique. Your journey is personal.

When we ask “Does being underweight or overweight affect fertility?”, we’re really asking how we can support our bodies better. And that starts with listening—really listening—to what your body is telling you.

Final Thoughts:

So, let’s answer the big question one more time: Does being underweight or overweight affect fertility? Yes, it can. But weight is just one part of a much bigger picture. And it’s something you can often improve with support, care, and the right tools.

Here’s what I hope you take away:

1. Your body is not broken.
2. Small changes can have big effects.
3. You are not alone in this.
4. It’s okay to ask for help.
5. You’re doing your best—and that matters.

Whether you’re on a journey to gain weight, lose weight, or simply understand your cycle better, you’re taking a beautiful, brave step toward growing your family. And that deserves to be celebrated.