In my previous post, I discussed why blood sugar balance matters in IVF. But behind many blood sugar issues lies a hidden problem called insulin resistance.
Insulin resistance can develop years before diabetes appears and may affect fertility long before blood sugar levels become abnormal. In fact, many people are told their glucose levels are “normal” whilst underlying metabolic dysfunction is already influencing hormone balance, egg quality and reproductive health.
What is insulin resistance?
Insulin is the hormone that helps move glucose from the bloodstream into cells where it can be used for energy. When cells become less responsive to insulin, the body compensates by producing more.
As a result, insulin levels can remain elevated for years whilst standard blood sugar tests still appear normal.
This is important because insulin doesn’t just regulate blood sugar. It also influences hormone signalling, inflammation, ovulation, egg development, implantation and early pregnancy.
How does insulin resistance affect fertility?
High insulin levels can disrupt the delicate balance of reproductive hormones.
Insulin resistance is commonly associated with PMOS (previously known as PCOS), but it can also occur in women who do not have PMOS and who maintain a healthy weight.
Research has linked insulin resistance with:
- Impaired egg quality
- Reduced embryo quality
- Increased inflammation
- Altered endometrial receptivity
- Reduced implantation potential
- Increased risk of early pregnancy loss
Some studies have even shown that insulin resistance may negatively affect embryo quality in women without PMOS undergoing IVF treatment.
The hidden problem
One of the challenges with insulin resistance is that routine screening may not identify it.
A normal fasting glucose or HbA1c does not necessarily mean that insulin function is optimal. These markers alone do not show how hard the pancreas is working to keep them within range. By the time blood sugar levels begin to rise, insulin resistance may have been developing for many years.
This is why assessing metabolic health requires looking beyond glucose alone.
Signs that insulin resistance may be present
Not everyone experiences symptoms, but common signs can include:
- Difficulty losing weight
- Increased abdominal fat
- Sugar cravings
- Fatigue after meals
- Energy crashes during the day
- Feeling faint, shaky or light-headed between meals
- Skin tags
- Darkened patches of skin around the neck, underarms or groin
- PMOS (previously known as PCOS)
- A family history of Type 2 diabetes
Supporting insulin sensitivity
The good news is that insulin sensitivity can often be improved through targeted lifestyle and nutritional interventions.
Helpful strategies include:
- Eating regular, balanced meals rather than grazing or snacking throughout the day
- Prioritising protein at meals
- Pairing carbohydrates with healthy fats and fibre
- Eating plenty of colourful vegetables and polyphenol-rich foods
- Regular movement throughout the day
- Walking after meals
- Resistance training
- Prioritising good-quality sleep
- Managing stress effectively
- Correcting nutrient deficiencies where appropriate
- Acupuncture, which may support metabolic health through its effects on stress regulation, inflammation and insulin sensitivity
Summary
Fertility is not just about reproductive hormones.
Egg quality, embryo development, implantation and healthy pregnancy all depend on good metabolic health. Insulin resistance can be present long before diabetes develops and may not be detected by routine screening.
This is why, in my practice, fertility investigations include a full metabolic work-up, looking beyond reproductive hormones alone to assess the factors that may be influencing fertility and IVF outcomes.
Identifying and addressing metabolic dysfunction before IVF creates an opportunity to optimise health, improve fertility potential and support the best possible treatment outcomes.
References
Huang, W., Chen, Q., Fan, Y., Ma, Y., Zhang, Y., Fang, T. & Wang, Y. (2021).
Association between insulin resistance and embryo quality in lean, non-PCOS women undergoing in vitro fertilization. Frontiers in Endocrinology, 12, 741981.
Full text:View article
Diamanti-Kandarakis, E. & Dunaif, A. (2012). Insulin Resistance and the Polycystic Ovary Syndrome Revisited: An Update on Mechanisms and Implications. Endocrine Reviews, 33(6), 981-1030.
Full text
Lei, R., Chen, S. & Li, W. (2024).
Advances in the study of the correlation between insulin resistance and infertility. Frontiers in Endocrinology, 15, 1288326. It reviews how insulin resistance may affect oocyte development, embryo quality, endometrial receptivity, implantation, assisted reproduction outcomes, miscarriage risk and pregnancy complications. Full text
Elder Cottage Clinic, Warton, PR4 