We often talk about metabolic health in the context of weight loss, but it has much broader applications — such as fertility. Many people struggling with infertility also have metabolic health problems . These can include hormonal imbalances, insulin resistance, obesity, and metabolic syndrome.
Scientists are still learning about the relationship between metabolic health and fertility, but a large body of evidence tells us that metabolic health is crucial to successful conception and a healthy pregnancy .
Does insulin resistance cause infertility?
Insulin resistance is known to be linked to infertility. When you have insulin resistance, your body produces more insulin (a hormone that regulates blood sugar levels) than it needs to get this job done. Eventually, the body does not respond normally to insulin and develops resistance to the hormone’s action, which leads to chronically elevated glucose levels .
When glucose dysregulation occurs like this, you may start to gain weight because the excess glucose is stored as fat that tends to gather around the abdominal area. Frustratingly, excessive weight gain only serves to exacerbate insulin resistance, leading to a vicious cycle that can be hard to break .
Weight gain due to insulin resistance can trigger the production of more estrogen, a female reproductive hormone, which throws off your body’s carefully balanced ratio of estrogen to testosterone .
It can also cause inflammation throughout the body, which can affect the reproductive system, specifically the function of the ovaries and testes (the main organs that produce sex hormones) .
Infertility in women
As a result of rising rates of insulin resistance and metabolic dysfunction, many women don't ovulate regularly or produce eggs at all anymore — both of which are necessary for conception . Insulin resistance is a leading cause of ovulatory dysfunction, which can lead to further hormonal imbalances and reproductive problems.
The hormonal disruption caused by insulin resistance may lead to a high level of androgens — i.e., testosterone and other male sex hormones, which can cause PCOS and infertility. There is evidence that insulin resistance contributes to recurrent miscarriage (miscarrying more than once) and polycystic ovarian syndrome (PCOS) in the mother, as well as low birthweight babies who have a higher risk of Type 2 diabetes later in life [8, 9].
Infertility in men
In men, fertility decreases when blood glucose levels are not well-regulated, which can often be the case when someone has insulin resistance.
Metabolism — especially glucose metabolism — and hormone balance in testicular cells is important to sperm health. In men, insulin resistance can cause lower total testosterone concentration and decreased sperm count and motility .
How obesity affects fertility
Obesity is another common cause of infertility in men and women [11, 12]. Weight gain and obesity-related inflammation can lead to an imbalance in sex hormones as they affect the way your body produces and regulates these hormones. On top of that, obesity can disrupt the signaling pathways and the function of various organs that produce sex hormones .
Women who are overweight or obese produce higher levels of estrogen and lower levels of progesterone than women with lower BMIs . This imbalance of crucial female sex hormones can lead to irregular ovulation cycles, make ovulation less likely to happen each month, and make it hard for sperm to reach the egg . Obesity is also an established risk factor for miscarriage . In fact, women who have a BMI greater than 27 are 3 times less likely to get pregnant than women with a healthy body weight .
In men, the risk of erectile dysfunction is much higher for obese individuals than for those who are not overweight . Obesity can decrease the production and quality of sperm, which is thought to be caused by chronic inflammation . Sperm from men who are obese are more likely to result in a miscarriage than sperm from men with lower BMIs, though the biological reason has not been well-established .
How does this tie back to your metabolic health? Research suggests that chronic inflammation in fat tissue can increase your risk of developing insulin resistance and type 2 diabetes .
We also know from studies that overweight and obese individuals tend to have impaired insulin sensitivity, which can lead to higher levels of glucose and insulin in the blood and promote increased fat storage in the liver. In other words, being overweight or obese can make you more insulin resistant, which can lead to even more weight gain — kicking off a negatively reinforcing cycle that potentially contributes to infertility.
That said, a low BMI doesn’t guarantee that you are metabolically healthy. While insulin resistance is the main way metabolic syndrome affects hormone and endocrine function — having a lower body weight does not mean you may not have issues with insulin production. Not producing enough insulin or cells resistant to insulin can lead to increased levels of testosterone in women and decreased testosterone levels in men . The implications for these can be PCOS in women and low sperm efficacy in men, as well as infertility for both.
How endocrine function affects fertility
Your endocrine system, which regulates hormones, can be drastically altered by metabolic syndrome — which in turn can cause problems with ovulation, sperm quality, fertilization, and embryo development . (Metabolic syndrome is characterized by the presence of obesity, insulin resistance, dyslipidemia, and hypertension.)
For example, women with metabolic syndrome may have a disrupted menstrual cycle due to higher levels of androgenic hormones (male hormones that can be converted into estrogen in women and help regulate menstruation) . On the other hand, other research indicates that men with metabolic syndrome have lower levels of testosterone than those who are not overweight, as well as an association with erectile dysfunction and premature ejaculation .
The relationship between PCOS, fertility, and metabolic health
Metabolic syndrome is a risk factor for PCOS, and the more severe the syndrome, the higher a woman’s risk of PCOS . It is well established that women with PCOS tend to have severe insulin resistance — even without obesity . The function of pancreatic beta-cells (where insulin is produced) is impaired in women with PCOS. A high percentage of body fat is associated with both insulin resistance and PCOS — though researchers are still determining which may come first, it is known that fat tissue is an endocrine organ that helps to regulate many aspects of metabolism .
Women with PCOS have higher than normal levels of androgens (male sex hormones), which can contribute to insulin resistance . Androgen excess can make women infertile by interfering with their ability to get pregnant in several ways:
- It causes an irregular menstrual cycle, preventing ovulation from occurring regularly.
- It makes it less likely that an egg will be produced when you do ovulate because your body produces fewer follicles each month.
- It can decrease the likelihood of successful fertilization of the egg by sperm.
Due to the strong relationship between PCOS and metabolic syndrome, weight loss and diet changes can be the first line of treatment to decrease symptoms and increase fertility . A great place to start is with foods rich in fiber, antioxidants, probiotics, and micronutrients (vitamins and minerals) — which can help limit drastic blood sugar spikes.
How metabolic health affects sperm count and quality
The impact of metabolic health on successful conception has been shown to be equally important in men . Recent research suggests that metabolic syndrome can drastically impact fertility in men, as obesity and related insulin resistance can lead to increased estrogen levels and reduced androgen levels .
Obesity and metabolic syndrome affect the quality of sperm directly, though there are many variables that may be responsible. Studies suggest that men with metabolic syndrome have lower sperm concentrations and reduced levels of semen volume (the amount produced during ejaculation).
Increased insulin resistance can be linked to lower sperm motility, as glucose is less available for sperm to use and survive . Cells within the testicles have specific mechanisms to sense glucose — dysregulation of glucose and insulin can impair the function of testicular cells . Both of these aspects combined mean that when you're trying to conceive, blood glucose regulation is crucial.
Other studies show an association between high blood pressure and low-quality semen production; both conditions may result from poor diet choices or other lifestyle factors related to obesity and metabolic syndrome. Oxidative stress related to metabolic issues has also been suggested as one mechanism for decreased sperm quality .
What you can do about insulin resistance and fertility
Overall, insulin resistance can lead to a cascade of events that can affect the reproductive system, leading to infertility in both men and women. However, research shows that improving insulin sensitivity leads to better fertility outcomes .
There are several modifiable lifestyle factors that you can focus on to increase sensitivity to insulin, regulate blood sugar levels, and improve your fertility. Reducing calorie intake by focusing on low-GI (and high-fiber) carbohydrates, colorful vegetables, lean proteins, and healthy fats such as olive oil — paired with increased physical activity — can increase fertility and conception rates in both men and women. Women who focus on healthier diet choices and increasing physical activity have been shown to have a better chance of conception, regardless of weight loss . Men who are more physically active produce healthier semen and have an anabolic hormonal balance that promotes fertility .
It’s important to remember that you have control over some aspects of your fertility. Certain lifestyle factors can increase or decrease your odds of getting pregnant. If you are concerned about your fertility, it is important to understand the role of diet and nutrition in the process.
- Even if you don’t have diabetes, insulin resistance, and blood glucose regulation can play a major role in fertility.
- Obesity is a major risk factor for infertility and can make it harder to get pregnant.
- It is important for hormones related to both reproduction and energy metabolism to be balanced and circulating at the right levels for fertility.
- Metabolic syndrome is a risk factor for PCOS—decreasing the risk of obesity and insulin resistance by monitoring your blood glucose levels can help lower your risk.
- Sperm count and quality are heavily impacted by metabolic health. The risk of infertility may also be lowered with a quality diet and blood sugar regulation.
Sarah Jayawardene is a nutrition and health writer focusing on metabolism and metabolic diseases. She has obtained a Bachelor’s degree in Biochemistry from Loyola Marymount University and a Master’s degree in Biochemical and Molecular Nutrition from Tufts University. Sarah is an avid baker, fiction reader, and dog mom.