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Excess weight affects female fertility

A good hormonal balance regulates the menstrual cycle. Overweight and obese women have higher levels of a hormone called leptin, which is produced in fatty tissue. This can disrupt the hormone balance and lead to infertility.

The quantity and distribution of body fat affect the menstrual cycle through a range of hormonal mechanisms. The more excess weight and the more abdominal fat, the greater the risk of fertility difficulties.

Excess weight, particularly excess abdominal fat, is linked to insulin resistance (when the body has to produce more insulin to keep blood sugar levels normal) and decreased levels of sex hormone-binding globulin (SHBG), a protein that is involved in the regulation of the sex-hormones androgen and estrogen.

This leads to irregular menstrual cycles, which in turn reduces fertility. Obese women have 20% less chnace of conceiving (66.4% of obese women conceive within 12 months, compared with 81.4% of women of normal weight).

This hormonal imbalance leads to anovulation (when no egg is released by the ovaries). Women with a body mass index (BMI) above 27 are have less chance to conceive because they don’t ovulate.

Many women who are obese still ovulate, but it appears the quality of the eggs they produce is reduced and even if they conceive, they are at higher risk for misscarriages.

This means that for a woman with a BMI of 35, the likelihood of getting pregnant within a year is 26% lower, and for a woman with a BMI of 40 it is 43% lower compared with women with a BMI between 21 and 29.

And even when couples use IVF to conceive, the chance of a live birth is lower for women who are overweight or obese than for women with normal BMI. On average, compared to women in the healthy weight range, the chance of a live birth with IVF is reduced by 9% in women who are overweight and 20% in women who are obese.

Excess weight affects male fertility

Obesity is also associated with lower fertility in Men. This is due to a combination of factors. These include hormone problems, sexual dysfunction and other health conditions related to obesity such as type 2 diabetes and sleep apnoea which are associated with lower testosterone levels and erectile dysfunction.

Carrying extra 10 kilos reduces male fertility by 10%.

Studies on the effects of paternal obesity on reproductive outcomes found obese men were more likely to experience infertility and less likely to have a live birth if they and their partner used IVF. This is because obesity not only reduces sperm quality, it also changes the physical and molecular structure of sperms.

The good news

While the facts about obesity and fertility can seem daunting, there is some good news too. Weight-loss interventions, particularly those that include both diet and exercise, can promote menstrual cycle regularity and improve the chance of pregnancy. In obese women with anovulatory infertility, even a modest weight loss of 5-10% improves fertility and chance of conceiving. Our expert team at Conceive IVF partners with you in this difficult journey of weight loss and walks you all the way till parenthood.

A weight loss of 7% of body weight and increased physical activity to at least 150 minutes a week of moderate intensity activity is recommended to improve the health and fertility of people who carry excess weight.

Lastly, men and women are twice as likely to make positive health behaviour change if their partner does too. So becoming pregnant will be more likely if you diet and exercise together.

Dr. Madhuri Roy

Dr. Madhuri Roy graduated as an MD in Obstetrics and Gynaecology in 2001 and completed her fellowship in Minimal access surgery (FMAS) from World Laproscopy Hospital. She is trained in Reproductive Medicine and endocrinology from prestigious Charles’s University of Czech Republic and is recognized by European society of Human Reproduction and Endocrinology (ESHREE) and European board of College of Obstretrics and Gynaecology (EBCOG).

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