What is the impact of obesity on male fertility?

What is the impact of obesity on male fertility?

Obesity, understood as a Body Mass Index (BMI) of over 30 kg/m2, is associated with various health problems: high blood pressure, diabetes, hypercholesterolemia, sleep apnoea, etc. One of the most important and least known aspects is the repercussions of male obesity on fertility.

In Spain, the estimated prevalence of obesity in the adult population (25-64 years) is 22.8% in men (20.5% in women), and increases with age.

According to a recent study, male obesity is associated with 20% of cases of male infertility and subfertility.

  • Men with obesity are associated with 20% infertility or subfertility

Why does it occur?

In the obese male, a conversion of the male hormone (testosterone) to oestrogen takes place, causing decreased levels of male hormone and gonadotropins. The consequence is a decrease in the quantity and quality of semen (the volume of the ejaculate, the number of spermatozoa and their mobility decrease, and morphological alterations appear in the sperm).

  • Obesity affects sperm quantity and quality.

Associated factors

  • Erectile dysfunction:

The presence of associated vascular disease and the hormonal alterations described above contribute to the appearance of erectile dysfunction in more than 30% of men with obesity (reaching 60% in some studies), making it difficult to achieve pregnancy naturally.

  • Up to 60% of obese men may suffer from erectile dysfunction
  • Diabetes:

Severe diabetes can lead to retrograde ejaculation in which semen is diverted into the bladder instead of out.

  • High blood pressure:

Some drugs used to control hypertension reduce the ability of the sperm to fertilise the egg.


Obese men are 3 times more likely to have oligozoospermia (low sperm concentrations) compared to men of normal weight.

La probabilidad de infertilidad en varones puede aumentar un 10% por cada 9kg de exceso de peso corporal.

  • Infertility in men is estimated to increase by 10% for every 9kg of excess weight

Assisted Reproduction Techniques in Male Obesity

The appearance in the early 1990s of intracytoplasmic sperm injection (ICSI) has allowed couples in which the male partner has poor semen quality or ejaculatory problems to achieve pregnancy. Recent studies have analysed the results of this type of treatment by comparing the results of treatments in which the male has a normal BMI with those in which the male has a high BMI, and it has been observed that excess weight can negatively affect the outcome of the treatment. In couples where the male partner is obese, the likelihood of achieving a full-term pregnancy is reduced.

Addressing the Problem of Infertility associated with Obesity

In order to increase the fertility rate in men, it is advisable to achieve a healthy and sustained weight loss through lifestyle changes and, if necessary, the use of drugs or bariatric surgery.

Adherence to the Mediterranean diet improves sperm concentration and motility and increases the likelihood of spontaneous pregnancy and after assisted reproductive techniques (1).

Weight loss is associated with an improved hormonal profile, improved semen quality and erectile dysfunction. It is estimated that there is a marked improvement in all parameters with a weight loss of 5-10%.

At this point we can consider the search for pregnancy with better expectations of success, either naturally or using Assisted Reproduction Techniques.

Being aware of the importance of leading a healthy life is necessary in order to have good physical and mental health and, as we have seen, a better reproductive prognosis.

Mª Carmen Tió, biologist at Instituto Bernabeu and Dr Pino Navarro, endocrinologist and director of our fertility endocrinology unit.


(1) Karayiannis et al., 2017: Association between adherence to the Mediterranean diet and semen quality parameters in male partners of couples attempting fertility


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