The link between weight and infertility
We know that conversations about weight can be sensitive, and we completely understand the emotions that come with them. For many, discussions around weight can bring up feelings of frustration, self-doubt, or even blame—but that’s not our goal here. Instead, we want to provide information that empowers you to make choices that support your overall health and fertility
First, we want to say that being very overweight or obese doesn’t mean you will have fertility issues. The interactions between obesity and infertility are complex and the information available can seem confusing and even conflicting. If you have been ‘large’ all your life, come from a family of bigger-than-average people, eat healthily, and exercise then you probably don’t have to worry. In fact most of us can point to a friend or relative who would have a high BMI but who has had no problems conceiving.
However, many other women (and men) who carry additional weight have trouble conceiving. Reproduction is intricately linked to energy balance via several hormones and cellular interactions, so getting that balance right can help with fertility.
Excess weight does not cause infertility – but often adds to the burden
Excess weight itself doesn’t directly cause infertility. Rather, the underlying factors that contribute to weight gain—such as hormonal imbalances, insulin resistance, and inflammation—can affect reproductive health. Being very overweight and having fertility issues are both outcomes of unbalanced hormones. So, when we talk about “obesity-related infertility” we mean exactly that – obesity and fertility are linked but your weight isn’t causing your infertility.
We know that statistically, obese women are more likely to not ovulate, have irregular menstruation, elevated risk of miscarriages, have greater difficulties with IVF, and decreased live birth rates so understanding the root causes and dealing with those is crucially important.
Relatively recent weight gain in adulthood can be a warning sign for future infertility
Those most at risk of obesity-related infertility tend to have been of regular weight when young and then had rapid weight gain after puberty or in early adult life. Obesity acquired in adulthood tends to be visceral fat (the fat that is around your middle and internal organs) which is more metabolically active, and which also induces inflammation in the body.
Adult weight (and the number of fat cells you have) in most situations is genetically determined. When we put on a large amount of weight, these fat cells enlarge in size. The resulting stretch of the fat cells causes the release of a number of pro-inflammatory signals (called adipokines) which influence the metabolism and also interfere with ovarian and reproductive function.
Insulin resistance driven by this pro-inflammatory state adds to the mix. A number of studies have shown the association of this pro-inflammatory visceral fat with ovulation, embryo function, implantation, and overall pregnancy outcomes.
Fat cells produce many hormones that also can affect fertility
Adipose tissue (ie fat cells) produces many hormones including:
- Leptin: Leptin has complex interactions with the reproductive function from stimulating puberty to suppressing estrogen in the sex organs, and influencing embryo implantation. Obesity is associated with high leptin levels which leads to a lack of sensitivity to the hormone – a condition known as leptin resistance. This means that your body loses its ability to regulate correctly so that you are likely to eat more and exercise less than your body actually needs, and so leading to more weight gain.
- Adiponectin is another hormone that the adipose (i.e. fat) tissue produces, which is known to have an impact on the regularity of ovulation and egg quality.
- Pro-inflammatory cytokines: Stretched fat cells also produce pro-inflammatory cytokines which can have a negative impact on ovulation and menstrual regularity.
- Sex hormone-binding globulin (SHBG): Visceral fat in the liver reduces sex hormone-binding globulin and increases the free androgen level which affects ovulatory function.
Being very overweight increases the risk of developing polycystic ovarian syndrome (PCOS)
The ‘cysts’ in PCOS aren’t the cause of fertility issues, rather they are the result of a complex set of hormonal interactions gone awry that can cause infertility.
PCOS is characterised by abnormal ovarian function due to insulin resistance and increased androgens (male hormones) in the blood. Obesity increases the risk of PCOS as the fat cells expand and excrete hormones which leads to a hormonal imbalance that disrupts the normal functioning of the ovaries.
These unbalanced hormones interfere with the development of ovarian follicles and timely ovulation causing delayed or irregular cycles, multiple ovarian cysts, and sometimes acne and unwanted facial and body hair growth. Additionally, women with PCOS have a higher risk of miscarriage and are more likely to develop gestational diabetes during pregnancy.
Obesity can impact procedures
At Flinders Fertility, egg retrievals are carried out at the Glenelg Day Surgery. This is a low-risk surgical day facility, and has restrictions on BMI and weight to protect patient safety. Complications with anaesthesia are much higher with obesity and anaesthetists require the full backup of a major hospital should the worst happen. This is for your own safety. While it pains us to have to do this, we would suggest that you choose a fertility clinic that uses Ashford Hospital or St Andrew’s Hospital for procedures. We can provide you with recommendations.
Obesity affects male fertility too
To be able to produce healthy sperm, the testes have to be cooler than normal body temperature at around 34-35C. It is common for men with obesity to have an excess of abdominal, inner thigh, and pubic area fat which can increase the scrotal temperature and inhibit the production of sperm2.
Additionally, increased temperature leads to DNA fragmentation and increased oxidative stress which in turn changes semen parameters and function resulting in infertility.
How to reverse weight-related infertility
Healthy Lifestyle
To enhance fertility in individuals with PCOS and obesity, we suggest prioritizing a healthy environment for both you and your future child. The initial 1000 days, extending from pre-conception to toddlerhood, is a critical period where proper nutrition can significantly affect a baby’s long-term health by lowering the likelihood of allergies, weight issues, and chronic diseases.
Rather than counting calories and focusing on weight loss, we recommend seeing a fertility dietitian who will consider your current situation, fertility goals , and timing and ensure that you are optimising your health. By shrinking fat cells through exercise and a healthy, but not restrictive diet, you can reverse metabolic changes and restore the balance of hormones.
Medication
When diet and exercise alone don’t work, treating the underlying metabolic conditions with medication can improve fertility. The most common medications are Metformin, Tirzepatide, Semaglutide, Liraglutide, or a combination of Naltrexone and Bupropion called Contrave.
It is important to note that these medications are not proven to be safe for conception and therefore use when trying to conceive is not recommended.
Seeking help
Reversing obesity is hard. Sometimes it feels like your body is working against you so rather than focusing on weight loss as an end in itself, we see more success in focusing on your overall wellbeing and that of your future child.
We recommend seeing a fertility dietitian for support. The Early Life Nutrition Alliance is a global group of fertility dietitians with a large member base in Australia. They offer telehealth consultations and can give you the extra support you may need. Check out their website to book an appointment.
If you have been trying to get pregnant for over 12 months, (or have been diagnosed with PCOS), we recommend that you make an appointment with our endocrinologist Associate Professor Vasant Shenoy. We can investigate the underlying issues to regulate any hormone imbalance that could be causing your weight gain and affecting your infertility and then make an achievable plan to get back into balance.
References
1. Adolescent body mass index and infertility caused by ovulatory disorders.
J W Rich-Edwards 1, M B Goldman, W C Willett, D J Hunter, M J Stampfer, G A Colditz, J E Manson in pubmed.ncbi.nlm.nih.gov/8030695/
2. Obesity, An Enemy of Male Fertility: A Mini Review.
Mohamed Ahmed Abd El Salam in Oman Medical Journal [2018], Vol. 33, No. 1: 3-6
Clinical Review by Associate Professor Vasant Shenoy