Obesity and Fertility: lets talk about it.

The excess of body fat, poor eating habits and other underlying conditions that compromise your hormones (including gut health) can contribute to a significant drop in fertility in women (as well as in men). With a concerning increase in women being diagnosed with Polycystic Ovary Syndrome (PCOS), currently affecting 10-15% women worldwide, the need for healthier food choices and weight management are vital not only for optimum fertility but also for a successful pregnancy.

Obesity during pregnancy has also been linked to an increased risk¹ for the fetus of preterm birth, macrosomia (a newborn much larger than average), perinatal death, and congenital abnormalities (including those affecting the neural tube). Furthermore the risk of miscarriage for a BMI over 30 can range from 25-37% in comparison to a normal-weight pregnancy.

Additionally, children born to obese mothers, amongst other consequences, present an increased risk to develop obesity, diabetes, kidney disease, high blood pressure, and cardiovascular diseases as adults.

¹ elevated risk of 1.8% to 25.3% (WHO)

Fertility: a family journey

When looking at pregnancy planning, food habits most definitely will be on top of the list especially when it comes to the expected supplements and foods-to-avoid list. In fact, studies showed in PCOS the food habits had a more important role in its management than exercise. But are we covering it all?

If you are planning for a baby (just started or have been trying), ensure this journey includes healthy food habits and wellbeing that will contribute to a healthy weight – including your partner’s. More than aesthetics and beyond our wellbeing, our body’s health at the time of conception can have a detrimental impact on your pregnancy or, in some cases, contribute to infertility.

To successfully improve eating habits and lifestyle, embracing a plan that will involve and bring in those you live with will support you and create a deeper, meaningful level of accountability. Think long-term.

Decreased sperm and semen quality are found to be decreased in obese male. Moreover, levels of testosterone seem to be also affected which impact fertility. Would this mean you partner, yourself, a donor – it is not only up to one person to bring health to an optimum fertility level.

Obesity , adipose tissue and hormones

Obesity is currently classified as someone with a BMI >30 kg/m² and implies an excessive or abnormal accumulation of adipose tissue. This same fat tissue, more than a storage of fat as an energy reserve, is capable of producing substances (cytokines) that have the potential to negatively impact sexual hormones and biological cycles. Furthermore, the disfunction caused by an excess of adipose tissue will also affect the metabolism of fats, food intake, body inflammation and insulin resistance.

One type of cytokines called adipokines have been linked to lower infertility. They include leptin, adiponectin and ghrelin – hormones previously discussed in one of my previous posts.

Leptin: an increase of adipose tissue leads to increased levels of leptin that will impar the body’s natural feedback mechanism involving appetite and add on to increased insulin resistance which is likely to be already present in obese individuals. It has also been reported that it can affect the secretion of Luteinizing Hormone (LH) – which is crucial for ovulation to occur.

Infertility & Obesity

Studies in women opting for Assisted Reproductive Technology (ART) to address infertility showed that an increase of 1 unit in their BMI decrease the probability of embryo implantation via ART by 2.2% – 4.3%. In fact, the National Institute for Health and Care Excellence (NICE) guidelines highlights how obesity may impact fertility and recommends weight loss advice to be provided. In fact, when looking at fertility treatments’ criteria, the vast majority has a BMI between 19 and 30 as a requirement.

Figure description: Effects of obesity on the hypothalamic-pituitary-ovarian axis, oocyte maturation, embryo, and fetal development.

Source: Yong, W. et al. “Role of Obesity in Female Reproduction”; Int J Med Sci. vol. 20. 2023.

Nutrition and Lifestyle

Weight loss (in obese/overweight individuals) is beneficial by reducing fat tissue, insulin levels and balancing hormones. It is actually what fertility treatments should have a primary treatment (as studies support) which is translated to a caloric restriction and/or increasing physical activity.

Gut Health: whilst studies are still undergoing in search for links between the bacteria that lives in our gut and the onset of obesity, it is known that the gut flora differs between individuals who are obese from those with normal weight. An unbalanced gut can, in fact, impact the fetus’ metabolism at mid-gestation and increase the risk of metabolic dysfunction in offspring. In sum, our gut health can impact fertility levels, the duration of the pregnancy and the baby’s health.

Promoting the consumption fermented foods² and a fibre-rich diet alongside limited consumption of sugars and processed foods are on the list of checks when addressing fertility and maintaining a healthy body and weight.

²Prior to the pregnancy (further nutritional advice required during pregnancy regarding which fermented foods are safe to consume).

Lifestyle: as part of a weight loss plan, addressing Life habits (from sleeping to levels of exercise and stress levels) will not only promote biological changes in the body towards losing weight and improve metabolic health, but also set a good pace for a healthy pregnancy (and baby!).

To find more about fertility (including infertility treatments) please visit British Fertility Society under “quick guides”.