Obesity and Fertility for Men and Women

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Did you know that your weight can affect your fertility? If you or your partner is overweight or obese, you may have lower chances of getting pregnant.

Studies have found that obesity may negatively affect fertility, not only in women but also men. In addition, an obese woman with an overweight or obese male partner has up to a two-fold further loss in fertility than their obese counterparts with normal weight partners. This also affects the effectiveness of fertility treatment.

Overweight and obesity are characterised by an excess of fat mass and are most commonly defined by the ratio between weight (kg) and the square of the height (m), which is known as BMI. The World Health Organisation (WHO) considers persons with a BMI over 25 kg/m² as overweight, and those with BMI over 30 kg/m² as obese. For Asians, due to our smaller physical built, persons with BMI over 23 kg/m² are considered as overweight and BMI over 25 kg/m² as obese.

Did you know about what is your BMI? Here’s how to calculate:

BMI = Weight (kg)

Height (m²)

How does obesity affect the fertility?

The mechanisms of how obesity reduces pregnancy rates are complicated and likely multi-factorial. The excess body fat tissues seem to play a major role as it impairs the secretion and metabolism of sex hormones.

Women who are obese have relatively higher level of androgen (male hormone), irregular ovulation or anovulation (no egg release from the ovaries) which leads to irregular menses. Even for those with normal ovulation, the pregnancy rate will be lower, probably due to poorer quality of the egg or a defect in endometrial receptivity. In a study that involved 3,000 women with normal ovulation, the probability of spontaneous conception declined with a BMI over 29 kg/m² and every one unit increase in BMI resulted in a four per cent reduction in the likelihood of conception.

For men, being overweight or obese is associated with lower levels of the male hormone (testosterone). This impairs semen quality, negatively affect sperm concentration and total motile sperm count. Apart from that, obese men may also be affected by decreased libido and erectile dysfunction.

What can you do?

The best treatment to obesity-related-infertility is to lose weight before trying on assisted reproductive techniques or drugs that help in induction ovulation.  Reduction of body weight has shown improvements in reproductive functions. Do not worry too much about having to achieve your ideal body weight, instead, focus on reducing weight. A modest reduction of 5 to 10 per cent of initial body weight is enough to show improvement in fertility. The best way for weight reduction is through lifestyle modification which involves proper dieting and regular exercise:

  1. Base your meals on starchy food such as rice, bread and noodle, choose whole-grains if possible

  2. Have at least five portions of fruits and vegetables each day

  3. Include some healthier protein at each meal for a longer satiety, such as fish, chicken breast, egg white and tofu

  4. Watch your portion size for each meal and snack, try not to eat in between meals if you are not hungry

  5. Decrease fat intake by choosing low-fat products, limiting deep-fried foods and any other food rich in cream, butter or margarine

  6. Watch what you drink. Other than carbonated drinks, fruits drinks, tea drinks, coffee and other flavored drinks may contain a lot of sugar too

  7. Minimise sedentary activities such as sitting for long hours in front of computer or television for a long time or taking lengthy afternoon naps

  8. Build activities into daily life, e.g. take the stairs instead of the lift or walk to nearby shop instead of driving

  9. Plan for regular exercise or participate in games that you like

For more information and personalised advice, see your dietitian today.


  1. Michigan State University. 2009. Obesity Significantly Cuts Odds Of Successful Pregnancy, Study Finds. ScienceDaily.
  2. Hammoud AO, Meikle AW, Reis LO, Gibson M, Peterson CM, Carrell DT. 2012. Obesity and male infertility: a practical approach. Semin Reprod Med. 30(6):486-95.
  3. Hammiche F, Laven JS, Twigt JM, Boellaard WP, Steegers EA, Steegers-Theunissen RP. 2012. Body mass index and central adiposity are associated with sperm quality in men of subfertile couples. Hum Reprod. 27(8):2365-72.
  4. American Dietetic Association. 2009. Position of the American Dietetic Association and American Society for Nutrition: Obesity, Reproduction, and Pregnancy Outcomes. J Am Diet Assoc. 109:918-927.
  5. Robert J.Norman, Manny Noakes, Ruijin Wu, Michael J.Davies, Lisa Moran & Jim X.Wang. 2004. Improving reproductive performance in overweight/obese women with effective weight management. Human Reproduction Update. Vol.10, No.3 pp. 267±280.