Fertility And Weight Loss
Weight can influence our reproductive hormones. Fat, otherwise known as adipose tissue, is an endocrine organ meaning that among other things, it is responsible for the production and release of hormones.
Having large amounts of body fat can change the balance of some of our hormones. Women with a very high BMI have been found to have higher leptin levels, the hormone which is produced by fat cells. This can lead to changes in levels of other reproductive hormones such as oestrogen which can lead to irregular periods and problems with ovulation and means that for people with a BMI of 30 kg/m2 or over it is likely to take longer to conceive (1).
Increased weight is also associated with inflammation and oxidative stress, which can reduce egg quality. Having good egg quality is important for the likelihood of fertilisation by a sperm as well as successful embryo implantation (2). Being overweight when pregnant can also increase the risk of miscarriage (3,4).
Weight also affects male fertility. Men who have a BMI of 30 kg/m2 or over are likely to have reduced fertility (5) due to effects on semen quality, sperm production and reduced sperm motility. Maintaining a normal weight is one of the effective ways to improve male fertility (6) for natural conception as well as when undergoing assisted conception (7).
Losing weight – effects on fertility
Losing weight via diet and exercise will likely regulate periods, increase the chance of ovulation, reduce inflammation and oxidative stress increasing overall chances of conception (1).
For both men and women, disrupted levels of reproductive hormones, such as sex hormone binding globulin, follicle-stimulating hormone, and testosterone have also been linked to being of a higher weight, resulting in infertility. Losing weight can help to improve sex hormone profile (8,9).
The chances of achieving a pregnancy through IVF decrease with each unit increase in BMI (10). Aiming for a weight within a healthy range for you can help to improve the chances of conception both naturally and through artificial reproductive technologies (11).
Nutritional value of a weight loss diet
When losing weight at any time but particularly when with fertility in mind, it is important to consider the journey being taken to lose weight.
The nutritional density of our diet is also very important when it comes to fertility outcomes and so while a very restrictive diet or more extreme measures such as bariatric surgery may be beneficial for initial weight loss they can also risk nutritional deficiencies which in itself can hinder the probability of a successful conception.
Considering and optimising the nutritional content of a lower calorie diet is important to ensure that you are receiving all of the fertility promoting nutrients required for optimal fertility outcomes and to lose weight in a healthy way. Combining dietary changes with increased activity is recommended for people of a higher weight to improve their fertility outcomes (10).
Losing too much weight
While reducing weight can be an important aim for some people when thinking about trying to conceive, it is important to understand the consequences of too much weight loss or having too little body fat, on fertility.
Having too low a BMI, losing too much weight or over exercising can also affect our reproductive hormones by reducing the amount of oestrogen. This can lead to a lack of or irregular menstrual cycles which is a sign that ovulation is not occurring regularly. Low oestrogen can also cause problems with implantation, ultimately reducing chances of conception.
If you are able to conceive, having too low a BMI or too high a BMI can also cause issues during pregnancy. These include increased risk of miscarriage, preterm birth and having a baby with a low birth weight. Therefore having strategies to maintain a healthy weight are important not just for fertility outcomes but going forwards as well.
Recommendations for a healthy weight for fertility
Aiming for a BMI of between 19 and 30 is optimal for fertility.
Tips for maintaining weight loss while also optimising your diet for fertility include:
- Choose whole grain or higher fibre carbohydrates
- Fill half of your plate with vegetables
- Drink at least 2L of water per day
- Avoid sugar sweetened drinks
- Partake in low to moderate intensity activity daily
- Exercise portion control
- Reduce foods high in sugar and saturated fat
- Fertility: assessment and treatment for people with fertility problems [Internet]. 2013 [cited 2021 May 27]. Available from: www.cla.co.uk].
- Talmor A, Dunphy B. Female obesity and infertility. Best Pract Res Clin Obstet Gynaecol [Internet]. 2015 May 1 [cited 2021 May 27];29(4):498–506. Available from: https://pubmed.ncbi.nlm.nih.gov/25619586/
- Sun YF, Zhang J, Xu YM, Cao ZY, Wang YZ, Hao GM, et al. High BMI and Insulin Resistance Are Risk Factors for Spontaneous Abortion in Patients With Polycystic Ovary Syndrome Undergoing Assisted Reproductive Treatment: A Systematic Review and Meta-Analysis [Internet]. Vol. 11, Frontiers in Endocrinology. Frontiers Media S.A.; 2020 [cited 2021 May 27]. Available from: https://pubmed.ncbi.nlm.nih.gov/33343510/
- Cavalcante MB, Sarno M, Peixoto AB, Araujo Júnior E, Barini R. Obesity and recurrent miscarriage: A systematic review and meta-analysis [Internet]. Vol. 45, Journal of Obstetrics and Gynaecology Research. Blackwell Publishing; 2019 [cited 2021 May 27]. p. 30–8. Available from: https://pubmed.ncbi.nlm.nih.gov/30156037/
- Sundaram R, Mumford SL, Buck Louis GM. Couples’ body composition and time-to-pregnancy. Hum Reprod [Internet]. 2017 Mar 1 [cited 2021 May 25];32(3):662–8. Available from: https://pubmed.ncbi.nlm.nih.gov/28158570/
- Wang S, Sun J, Wang J, Ping Z, Liu L. Does obesity based on body mass index affect semen quality?—A meta‐analysis and systematic review from the general population rather than the infertile population. Andrologia [Internet]. 2021 May 24 [cited 2021 May 27]; Available from: https://onlinelibrary.wiley.com/doi/10.1111/and.14099
- Campbell JM, Lane M, Owens JA, Bakos HW. Paternal obesity negatively affects male fertility and assisted reproduction outcomes: A systematic review and meta-analysis [Internet]. Vol. 31, Reproductive BioMedicine Online. Elsevier Ltd; 2015 [cited 2021 May 27]. p. 593–604. Available from: https://pubmed.ncbi.nlm.nih.gov/26380863/
- Slopien R, Horst N, Jaremek JD, Chinniah D, Spaczynski R. The impact of surgical treatment of obesity on the female fertility [Internet]. Vol. 35, Gynecological Endocrinology. Taylor and Francis Ltd; 2019 [cited 2021 May 25]. p. 100–2. Available from: https://www.tandfonline.com/doi/abs/10.1080/09513590.2018.1500536
- Crosignani PG, Colombo M, Vegetti W, Somigliana E, Gessati A, Ragni G. Overweight and obese anovulatory patients with polycystic ovaries: Parallel improvements in anthropometric indices, ovarian physiology and fertility rate induced by diet. Hum Reprod [Internet]. 2003 Sep 1 [cited 2021 May 27];18(9):1928–32. Available from: https://pubmed.ncbi.nlm.nih.gov/12923151/
- Best D, Avenell A, Bhattacharya S. How effective are weight-loss interventions for improving fertility in women and men who are overweight or obese? A systematic review and meta-analysis of the evidence. Hum Reprod Update [Internet]. 2017 Nov 1 [cited 2021 May 27];23(6):681–705. Available from: https://pubmed.ncbi.nlm.nih.gov/28961722/
- Espinós JJ, Solà I, Valli C, Polo A, Ziolkowska L, Martínez-Zapata MJ. The effect of lifestyle intervention on pregnancy and birth outcomes on obese infertile women: A systematic review and meta-analysis [Internet]. Vol. 14, International Journal of Fertility and Sterility. Royan Institute (ACECR); 2020 [cited 2021 May 27]. p. 1–9. Available from: /pmc/articles/PMC7139226/
- McGrice M, Porter J. The effect of low carbohydrate diets on fertility hormones and outcomes in overweight and obese women: A systematic review [Internet]. Vol. 9, Nutrients. MDPI AG; 2017 [cited 2020 Sep 11]. Available from: /pmc/articles/PMC5372867/?report=abstract