Are “Plus-Size Women” More Likely to Conceive? The Science Behind Body Weight and Fertility

In a society increasingly defined by body-image anxiety, women’s weight has become a subject of constant scrutiny—not only for aesthetic reasons but also in relation to health and fertility. Scientific research has shown that body weight, for both women and men, plays an important role in conception success. However, this relationship is not a simple matter of “the lighter, the better.” What truly matters is maintaining a healthy body mass index (BMI).

1. The Relationship Between Body Weight and Female Fertility

In 2015, researchers at the University of Utah School of Medicine published a study examining the correlation between female BMI and in vitro fertilization (IVF) success rates 【Figure 1】. The findings revealed that both underweight and overweight women had lower IVF success rates, while the highest pregnancy rates occurred among women with a BMI between 23 and 24.

For example, a woman who is 160 cm tall would have an optimal weight between 58–61 kg, while a woman who is 170 cm tall would ideally weigh 66–69 kg.
From a fertility perspective, this data indicates that the popular “slim and petite” body ideal actually works against natural fertility.

(1) Effects of Being Underweight

When body fat levels are too low, the hypothalamic–pituitary–ovarian axis may become suppressed, resulting in irregular menstrual cycles or anovulation (lack of ovulation), both of which significantly reduce the likelihood of conception.

(2) Effects of Being Overweight

Conversely, excessive body weight can cause insulin resistance and hormonal imbalance, leading to conditions such as polycystic ovary syndrome (PCOS) and poor endometrial receptivity. These disruptions increase the risk of ovulation disorders and implantation failure.

In short, whether too thin or too heavy, hormonal fluctuations involving estrogen, progesterone, and insulin can impair ovarian function and alter the uterine environment, making conception more difficult.

From a reproductive health standpoint, “plus-size” women often possess physiological advantages over those who are extremely thin.

2. How Male Body Weight Affects Fertility

Body weight is not just a women’s issue — men’s weight also influences reproductive potential. Another study from the University of Utah 【Figure 2】 found that overweight and obese men tend to have lower sperm quality, reflected in:

Reduced sperm motility;

Higher rates of abnormal sperm morphology;

Increased sperm DNA fragmentation.

The biological explanation lies in hormonal disruption: excess body fat reduces testosterone levels, while aromatase enzymes in fat tissue convert more androgens into estrogen, disturbing the hormonal balance necessary for healthy sperm production.

Although male weight affects conception within a wider margin of tolerance than female weight, research indicates that moderate exercise and weight management can significantly improve sperm quality and IVF success rates.

3. Maintaining a Healthy Weight Builds the Foundation for Conception

It is therefore clear that maintaining an optimal weight for both partners provides a strong foundation for successful conception.

For women, body weight primarily influences ovarian function and uterine health, while for men, it affects sperm vitality and DNA integrity.

A balanced body composition improves not only the chances of natural conception but also the outcomes of assisted reproductive technologies.

4. Other Lifestyle Factors That Affect Fertility

Beyond body weight, everyday lifestyle habits play a crucial role in reproductive success. Couples planning for pregnancy should pay attention to the following aspects:

Balanced diet: Increase intake of folic acid, high-quality protein, and vitamins. Reduce consumption of sugary, fatty, and salty foods.

Regular exercise: Engage in moderate-intensity aerobic activity to enhance metabolism and hormonal stability.

Healthy sleep: Maintain consistent sleep patterns to support hormonal balance.

Avoid smoking and alcohol: Nicotine and alcohol can impair both egg and sperm quality.

Stress management: Chronic stress can disrupt hormone secretion, leading to ovulatory dysfunction and reduced sperm production.

These seemingly minor habits, when sustained, are more natural and safer than medical intervention — and they lay the groundwork for a healthy pregnancy.

5. Conclusion

In summary, both partners’ body weight plays a key role in determining fertility outcomes.

For women, weight affects ovulation, hormone regulation, and uterine receptivity.

For men, weight impacts sperm quantity, motility, and DNA integrity.

Alongside weight management, maintaining a healthy diet, regular exercise, proper rest, and a positive mindset are equally essential.

For couples preparing for pregnancy, achieving a balanced body weight and optimizing lifestyle habits are vital first steps toward a healthy and successful conception.