Fertility and Excess Weight: What Really Prevents Conception

One in five couples in Ukraine faces difficulties conceiving. While there can be many causes, one of the most common often goes unnoticed. We're talking about excess weight.

Not just "a few extra kilograms." But how adipose tissue transforms into an active hormonal organ that interferes with the body's most intimate processes.

How Weight is Connected to Reproductive Health

Adipose tissue is not a passive energy storage. It's an endocrine organ that produces hormones and affects metabolism. And when there's too much of it, it begins to "command" the reproductive system.

Here's what happens. In adipocytes, fat tissue cells, the enzyme aromatase actively works. It converts androgens to estrogens. The more adipose tissue, the more estrogen is produced outside the ovaries [32]. Excess estrogen disrupts hormonal balance, which can lead to irregular menstruation and ovulation problems.

But estrogen isn't the only player. Adipose tissue also produces leptin, the satiety hormone. In people with obesity, leptin levels are elevated, but leptin resistance develops. This affects the hypothalamic-pituitary-ovarian axis and disrupts ovulation [32].

Genes matter too. Research has found that FTO and Lep genes simultaneously affect both lipid metabolism and reproductive function through shared neuroendocrine pathways in the hypothalamus [36]. That is, predisposition to obesity and fertility problems may have common genetic roots.

Obesity and Female Fertility: From Irregular Cycles to Anovulation

The connection between excess weight and female fertility is best illustrated by polycystic ovary syndrome, or PCOS. According to WHO data, PCOS affects approximately 7-10% of women of reproductive age [42].

The numbers are striking. US studies show that among women with PCOS, about 60% have obesity. And 87.5% have BMI over 26 kg/m², which is almost twice the rate in the general population [30]. Though statistics differ across countries — in an Italian study only 14% of women with PCOS had obesity, while in a Korean study it was about 20% [30].

Why is this important? Because the connection works both ways. Obesity worsens PCOS symptoms, and PCOS promotes weight gain. It's a vicious cycle.

Elevated androgen levels, characteristic of PCOS, are often combined with insulin resistance and obesity [39]. Excess androgens in women are associated with metabolic disorders, and fertility is disrupted through several mechanisms: infrequent ovulation or complete anovulation [39].

But there's good news. A 2024 meta-analysis showed that bariatric surgery in women with PCOS and obesity reduces menstrual irregularity, decreases ovarian volume and free testosterone levels [35]. And weight loss after bariatric surgery improves spontaneous ovulation frequency 2.5 times compared to conservative treatment [37].

Metformin also shows effectiveness. A meta-analysis of 12 studies involving 683 patients found significant reductions in BMI, waist circumference, FSH, LH and testosterone levels in women with PCOS and obesity on metformin [35].

Obesity and Male Fertility: Testosterone, Sperm, and DNA

Men with obesity also face reproductive problems. And it's not just about reduced libido.

A recent 2025 meta-analysis including 14 studies and 8,443 men showed a clear relationship. Men with overweight and obesity had significantly worse sperm parameters: normal morphology, total motility, concentration, progressive motility, and total sperm count [3].

And it's not just about sperm. The same meta-analysis found statistically significant differences in sex hormone levels: total testosterone, FSH and LH differed between normal weight, overweight and obesity groups [3].

High BMI can reduce sperm count, motility, morphology and testosterone levels [4]. Progressive sperm motility, which is closely linked to pregnancy probability, is often impaired in obese men [4]. Additionally, obese men more frequently suffer from erectile dysfunction and reduced libido [4].

And there's DNA damage. In obese men, increased levels of reactive oxygen species cause sperm DNA damage. This can lead to mutations, chromosome fragmentation and overall sperm quality loss, complicating pregnancy achievement [19]. Moreover, these negative effects reduce the success of assisted reproductive technologies, particularly IVF [19].

Weight loss through lifestyle changes increases testosterone levels. However, it remains unclear whether this leads to improved fertility outcomes [4]. Further research is needed.

Weight and Pregnancy Course: Risks for Mother and Baby

If pregnancy occurs, excess weight continues to affect health. And the risks are substantial.

A 2025 study showed: mothers with overweight have 2.15 times higher risk of preeclampsia and 1.61 times higher risk of gestational diabetes compared to normal-weight women [10]. Meanwhile, chances of normal vaginal delivery decrease by 42% [10].

Meta-analyses from 2024-2025 give even more precise estimates: maternal obesity is associated with a 2-3-fold increased risk of preeclampsia, gestational diabetes and cesarean delivery. For women with class III obesity, the risk of ICU admission increases up to 5 times [8].

Here's the complete list of complications associated with obesity during pregnancy [8]:

• Gestational diabetes
• Preeclampsia
• Miscarriage
• Unexplained stillbirth
• Anesthetic complications
• Cesarean delivery
• Prolonged labor induction
• Infectious complications
• Thromboembolic events

What about the baby? Fetuses of obese women during pregnancy have increased risk of excessive growth, birth defects, stillbirth and preterm delivery [22]. And the impact doesn't end at birth — intrauterine exposure to maternal obesity may predispose the child to long-term health problems, potentially creating a cycle of obesity across generations [22].

Women with a history of gestational diabetes have significantly higher risk of developing type 2 diabetes after delivery: hazard ratio 6.07 [18].

Weight Loss Before Conception: What Science Says

Logic suggests: losing weight before pregnancy is better for everyone. But does science confirm this?

A 2024 systematic review and meta-analysis gave interesting results. Overweight or obese women who underwent weight loss interventions before conception had higher pregnancy rates. However, the impact on live birth rates and miscarriages was not statistically significant [1].

This doesn't mean weight loss is useless. The review authors note: there's no universal recommendation for preconceptional weight loss for overweight women. A personalized approach is needed [16].

At the same time, adverse pregnancy and perinatal outcomes associated with obesity pose serious risks for women and their offspring [16]. Therefore, weight loss before pregnancy still makes sense — even if it doesn't directly increase live birth chances, it reduces complication risks.

What Works for Weight Loss When Planning Pregnancy?

• Lifestyle changes: diet and physical activity remain the foundation. Regular exercise helps reduce insulin, glucose and androgen levels, improve menstrual regularity and ovulation [41].
• Pharmacological therapy: insulin-sensitizing medications, particularly metformin and GLP-1 receptor agonists, show effectiveness. A 2024 study in American Journal of Obstetrics and Gynecology showed that GLP-1 users with PCOS had nearly 20% improvement in insulin sensitivity over 6 months [29].
• Bariatric surgery: for women with severe obesity. But most recommendations advise waiting 1-2 years after surgery before attempting pregnancy [14]. This may not suit older reproductive-age women.

GLP-1 Agonists and Pregnancy Planning: What You Need to Know

Modern weight loss medications like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) have been true breakthroughs. But if you're planning pregnancy, there's critically important information.

GLP-1 agonists are not recommended for weight loss during pregnancy. And most should be discontinued if you're pregnant or trying to conceive [2].

Why? Human data is still limited. Early studies found no increased fetal risk compared to insulin. This is reassuring. But studies included only small numbers of pregnant women, and larger-scale research is needed [2]. Some animal studies showed potential offspring development problems [9].

Why is such a long period needed? Semaglutide remains in the body long after the last dose. The washout period ensures the drug is completely eliminated before conception [2].

And there's the interesting "Ozempic babies" phenomenon. Weight loss on GLP-1 agonists can restore ovulation and increase fertility in some women [2]. Meanwhile, tirzepatide may reduce oral contraceptive effectiveness through delayed gastric emptying [20]. This increases unplanned pregnancy likelihood.

What to Do If You Learn About Pregnancy While Taking GLP-1?

One early study showed that first-trimester GLP-1 agonist use didn't harm fetal development. This is reassuring. But the study included only 168 pregnant women [13]. More research is needed before we can confidently speak about safety.

If you're planning pregnancy and using weight loss medications, the best approach is specialist consultation. At DOZA, we support clients at all stages, including planning program exit and transitioning to pregnancy.

Path to Healthy Pregnancy: What You Can Do Today

Excess weight isn't a fertility death sentence. But it's also not a problem to ignore. Here's what science shows.

Obesity affects reproductive health through hormonal mechanisms that can be corrected. Adipose tissue produces excess estrogen and leptin, disrupting ovulation in women and sperm quality in men. Weight loss — even moderate — can improve hormonal balance.

For women with PCOS, weight loss is especially important. Weight loss improves menstrual regularity, reduces androgen levels and can restore ovulation. Bariatric surgery shows the best results, but conservative methods are also effective.

For obese men, weight loss may improve sperm quality and testosterone levels. While data on impact on final fertility outcomes remains mixed, improved sperm parameters is already a positive step.

Before pregnancy, weight loss reduces complication risks: gestational diabetes, preeclampsia, cesarean delivery. This is important for both mother and baby's health.

If you're using modern weight loss medications, plan pregnancy well in advance. Drug washout periods are mandatory. And it's best done under specialist supervision.

Each situation is individual. Age, reproductive plans, comorbidities — all of this affects the optimal strategy. If you're planning pregnancy and want to lose weight first, or if you're already on a weight loss program and thinking about the future — talk to a specialist. We at DOZA are always ready to help plan this important step.