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Fertility and Weight Loss

Fertility and Weight Loss

Weight loss is about living a healthier, happier life. Why not? Losing those extra fats can indeed improve overall wellness. For many people – both men and women – it is also to increase the chances of getting pregnant. As it turned out, being overweight or obese has a negative implication on fertility. Read on to understand why that is so to have a better understanding of the science.

Infertility in Canada

The widely accepted definition of infertility is failure to conceive after one year or longer of unprotected sex. For women, fertility declines steadily with age. Hence the general recommendation for women 35 years or older is to consult with a reproductive endocrinologist if unable to get pregnant after six months of unprotected sex. Keep in mind, though, that infertility is not exclusive to women but also men.

In Canada, if you were to gather six couples together, there is a chance that one of them may have a fertility issue. 1 in 6 or 16% of couples experience infertility, a number that has doubled since the 80s (“Fertility”).

The cause of infertility in couples by gender are as follows:

  • 30% man
  • 40% woman
  • 20% both man and woman
  • 10% no reason found

There is no denying that infertility can take a toll on relationships, negatively impacting emotional and psychological well-being. The cost of treatments can also place a heavy burden on finances.

Overweight and Obesity in Canada

On weight, healthcare professionals refer to the body mass index (BMI), a calculation based on an individual’s height and body mass.

BMI = weight / height in meter squared

A person with BMI ranging from 18.5 to 24.9 is healthy and most ideal. If it falls between 25 to 29, that person is overweight. At 30 and above, that person is obese.

Overweight and obesity are a long-standing concern in Canada. Consider these figures in 2018 (“Overweight and Obese Adults, 2018”):

  • 8% or 7.3 million Canadian adults (18 years and older) are obese
  • 3% or 9.9 million Canadian adults are overweight

The numbers are staggering. A combined 63.1% of the population are either overweight or obese. Although there is no evidence, perhaps it could be one factor contributing to the continuous decline of the fertility rate in Canada (“Canada Fertility Rate 1950-2020”).

Canada’s fertility rate (births per woman) over the last four years:

  • 2021: 1.500
  • 2020: 1.509
  • 2019: 1.517
  • 2018: 1.525

A fertility rate of 2.1 is a must for the population to stay stable. It has been half a century since Canada met this threshold. At the present course of 1.5, the number of new births is not enough to replace the current population. It is the reason why the government introduced measures to accept 401,000 new permanent residents in 2021.

Fertility and Weight

Discussing the causes of infertility among men and women and treatment options is beyond this article’s scope. In particular, our focus is on weight (body fats) and how it affects fertility.

Infertility in Overweight or Obese Women

Overweight and obese women need more time to conceive. Furthermore, obesity increases the risk of infertility threefold compared to non-obese women (Silvestris et al.). The difficulties in getting pregnant are due to unhealthy weight, causing hormonal imbalances, inability to release an egg from ovaries, and menstrual disorders.

For women seeking assisted reproduction, excess weight negatively impacts intracytoplasmic sperm injection (ICSI), in-vitro fertilization (IVF), and ovulation induction.

Note: Polycystic ovary syndrome (PCOS), which causes low fertility or infertility, is an obesity-related condition.

Infertility in Overweight or Obese Men

Every single-point increase in BMI causes a 2% testosterone decrease (Travison et al.). The waistline is, too, a factor, with every 4-inch increasing the chances of low testosterone level by 75% (Svartberg et al.).

Compared to men with normal BMI, being overweight increases the chances of low sperm count (oligozoospermia) by 11%, no sperm in the ejaculate (azoospermia) by 39%. In obese men, the chances of low sperm count increase by 42%, and no sperm in the ejaculate by 81% (Sermondade). Mainly, this is due to a prime hormonal defect leading to the inability to maintain testosterone concentrations (Katib). Consequently, it negatively impacts the production of sperm.

Erectile dysfunction (ED) is another condition that may arise. For instance, having a BMI of 28 increases the chances of developing this condition by 90% (Garimella et al.).

infertility and weight

Weight Loss and Fertility

There are hundreds of studies on the negative impact of being overweight and obese on health, including fertility. The logical assumption is that for such people to be fertile, they have to lose weight. Indeed, a study shows that much. Losing even only 5% to 10% of body weight can already restore fertility (Balen and Anderson).

Particularly for women, PCOS can be the cause of overweight or obesity. The imbalance in reproductive hormones prevents ovaries from releasing an egg. For women trying to get pregnant, that difficulty does not end there. PCOS also causes insulin resistance that stops ovulation because the ovaries produce less estrogen and more testosterone.

With a BMI of 25 or above, weight loss greatly benefits women’s fertility – and men, too. It is also commonly believed that it helps improve the success rate of fertility treatments. However, recent studies suggest the improvements may not be as significant as previously thought (Gaskins). The focus, therefore, should not merely be about losing weight but also following a healthy diet. It is a must because there is also the entire pregnancy period to consider.


“Fertility.” Government of Canada, 2013,

“Overweight and Obese Adults, 2018.” Statistics Canada, Government of Canada, 25 June 2019,

“Canada Fertility Rate 1950-2020.” Macrotrends,

Silvestris, Erica, et al. “Obesity as Disruptor of the Female Fertility.” Reproductive Biology and Endocrinology, vol. 16, no. 1, 9 Mar. 2018, 10.1186/s12958-018-0336-z.

Travison, Thomas G., et al. “The Relative Contributions of Aging, Health, and Lifestyle Factors to Serum Testosterone Decline in Men.” The Journal of Clinical Endocrinology & Metabolism, vol. 92, no. 2, Feb. 2007, pp. 549–555, 10.1210/jc.2006-1859. Accessed 10 Dec. 2019.

Svartberg, Johan, et al. “Waist Circumference and Testosterone Levels in Community Dwelling Men. The Tromsø Study.” European Journal of Epidemiology, vol. 19, no. 7, July 2003, pp. 657–663,, 10.1023/b:ejep.0000036809.30558.8f. Accessed 2 Nov. 2019.

Sermondade, Nathalie. “Obesity and Increased Risk for Oligozoospermia and Azoospermia.” Archives of Internal Medicine, vol. 172, no. 5, 12 Mar. 2012, p. 440, 10.1001/archinternmed.2011.1382. Accessed 9 Jan. 2021.

Katib, Atif. “Mechanisms Linking Obesity with Male Infertility.” Central European Journal of Urology, vol. 68, no. 1, 2015, 10.5173/ceju.2015.01.435.

Garimella, Pranav S., et al. “The Association between Body Size and Composition and Erectile Dysfunction in Older Men: Osteoporotic Fractures in Men Study.” Journal of the American Geriatrics Society, vol. 61, no. 1, Jan. 2013, pp. 46–54, 10.1111/jgs.12073. Accessed 15 Oct. 2020.

Garimella, Pranav S., et al. “Association between Body Size and Composition and Erectile Dysfunction in Older Men: Osteoporotic Fractures in Men Study.” Journal of the American Geriatrics Society, vol. 61, no. 1, Jan. 2013, pp. 46–54, 10.1111/jgs.12073. Accessed 15 Oct. 2020.

Balen, Adam H., and Richard A. Anderson. “Impact of Obesity on Female Reproductive Health: British Fertility Society, Policy and Practice Guidelines.” Human Fertility, vol. 10, no. 4, Jan. 2007, pp. 195–206, 10.1080/14647270701731290. Accessed 13 Dec. 2019.

Gaskins, Audrey J. “Recent Advances in Understanding the Relationship between Long- and Short-Term Weight Change and Fertility.” F1000Research, vol. 7, 26 Oct. 2018, p. 1702, 10.12688/f1000research.15278.1. Accessed 8 Oct. 2020.