Weight Loss and Fertility: Your Questions Answered

Trying to conceive (TTC) can come with a LOT of questions — and if you’re wondering how weight loss and fertility connect, you’re definitely not alone. Let’s break it down with clear, evidence-backed answers so you can understand how your body, weight, and fertility work together, and what (if anything) you should do if weight is on your mind while TTC.

Does weight loss affect fertility?

Yes, weight loss can impact fertility — but it’s not just about the number on the scale. Research shows that being in a weight range considered overweight or obese can affect ovulation (when your body releases an egg), hormone balance, egg quality, and even how your body responds to fertility treatments like IVF.

Some studies have found that weight loss in people with higher BMIs improved menstrual cycles and increased the chances of spontaneous conception (AKA, getting pregnant without medical help).

But here’s the key: weight is only one piece of the puzzle. Stress, sleep, nutrition, genetics, and underlying health conditions all play a role too.

Why is it easier to get pregnant after losing weight?

If you’ve ever heard someone say, “Just lose a bit of weight, and you’ll get pregnant,” you probably wanted to scream. It’s more complicated than that, but here’s the science behind why weight loss might help.

When someone is in a higher weight category, their body may have:

• More insulin resistance, which can throw off hormone signals and lead to irregular or missing periods.
• Higher levels of estrogen stored in fat tissue, which can disrupt the brain-ovary communication that controls ovulation.
• Increased inflammation, which can affect egg development, uterine lining, and implantation.

Losing even a small amount of weight (we’re talking 5–10% of body weight) can help regulate hormones, restart ovulation, and improve chances of conception — even before any fertility treatments come into play.

How much weight do I need to lose to help fertility?

Here’s some encouraging news: you don’t need to hit a “perfect” weight to see improvements.

Studies show that losing just 5–10% of your starting weight can:

• Restore regular ovulation in people with irregular or absent periods
• Improve insulin sensitivity
• Lower androgen (male hormone) levels in people with PCOS (polycystic ovary syndrome)
• Increase the likelihood of conception, both naturally and with treatments like IVF

Can weight loss improve egg quality?

Egg quality is shaped by lots of factors, with age being one of the biggest players — but weight matters too. Research has shown that in people with obesity, the ovarian environment can become less supportive, which affects how eggs mature. Inflammatory markers may also rise, potentially damaging egg health, and there’s an increased risk of poor embryo development after fertilization.

While weight loss can’t reverse the effects of aging, some studies suggest that improving overall metabolic health through weight loss may help create a better environment for eggs and embryos. That said, more research is still needed to fully understand how strong this connection is. If you’re going through fertility treatment, your doctor might recommend focusing on improving your overall health, including managing weight, to give your eggs the best possible chance.

What is the ideal BMI for getting pregnant?

This is where things get tricky. BMI (body mass index) is a common tool used in healthcare, but it’s not a perfect measure. It doesn’t account for muscle, body composition, or individual health differences.

That said, research often shows that people with a BMI between 18.5 and 24.9 have the highest fertility rates. However:

A BMI below 18.5 (underweight) can also cause fertility issues, including irregular or absent periods.

A BMI over 25 (overweight or obese) is associated with lower pregnancy rates, even with treatments like IVF.

BUT — and it’s a big but — plenty of people with higher or lower BMIs get pregnant. Fertility is never determined by BMI alone. Factors like age, egg reserve, hormone levels, sperm health, and lifestyle matter just as much (if not more).

Is it harder to get pregnant while dieting?

Dieting can be a double-edged sword when you’re trying to conceive. On the positive side, improving your nutrition, cutting back on ultra-processed foods, and staying active can support healthy weight loss and boost your overall reproductive health. But there’s a downside: overly restrictive diets or extreme workout routines can actually harm fertility.

Losing weight too quickly can disrupt your menstrual cycle, make your stress hormones like cortisol spike, and lead to nutritional deficiencies that affect both egg and sperm quality. Rapid weight loss or bouncing between diets (yo-yo dieting) can end up reducing your chances of getting pregnant. That’s why the focus should always be on building sustainable, balanced habits — not turning to crash diets or pushing your body to the extreme.

Does weight loss help with PCOS fertility?

For people with PCOS, even modest weight loss (again, 5–10%) can help lower androgen levels, improve insulin resistance, and restart ovulation. This can dramatically increase the chances of natural conception or improve the success of fertility treatments.

Do I need to lose weight before IVF?

Many clinics recommend aiming for a BMI under 35 before IVF, as higher BMIs are linked to lower success rates. But every clinic has different policies, and many will still work with people in higher BMI categories. Talk to your fertility team — they’ll help you create a plan that’s right for you.

Should I use weight loss medications when TTC?

Medications like GLP-1 agonists (e.g., semaglutide, known by brand names like Ozempic or Wegovy) are getting a lot of buzz for weight loss, but they’re not approved for use in pregnancy and should be paused before TTC. Always check with your doctor before starting or stopping any weight loss medications when planning a pregnancy.

What matters most: Balancing body and mind

Weight and fertility are deeply personal, and there’s no one-size-fits-all approach. While making small, sustainable weight changes can help, it’s only one piece of the bigger fertility picture. Just as important are caring for your mental health, finding ways to reduce stress, eating a balanced, nutrient-rich diet, moving your body in ways that feel enjoyable, and making sure you get enough sleep and rest. It’s also key to work closely with your healthcare provider to create a plan that’s tailored specifically to you.

If you’re feeling overwhelmed or unsure where to begin, reaching out to a fertility specialist, registered dietitian, or therapist who focuses on reproductive health can be a great step. You don’t have to figure this all out on your own.

Tassia O'Callaghan is an experienced content writer and strategist, having written about a vast range of topics from chemical regulations to parenting, for brands like Peanut App Ltd, Scary Mommy, Tally Workspace, and Fertility Mapper. She's an advocate for realistic sustainable living, supporting small businesses (author of A-Z of Marketing for Small Businesses), and equity across all walks of life. Follow her on LinkedIn or TikTok, or see more of her work on Authory or her website.