Weight and fertility
Have you ever wondered if your weight had an impact on your fertility? well, read on……..
The problem of obesity has reached epidemic proportions. More than half the women in the United states and United Kingdom are either overweight or obese. Malaysia appears no different. Obesity significantly affects fertility and reproduction in both males and females.
At present, the best method of determining the appropriateness of one’s weight is to measure their body mass index (BMI). Yes, some do argue that measuring the waist-hip ratio is as good, but unfortunately, most of the good data (from clinical studies) out there talks only of BMI.
What is BMI?
This is a simple mathematical equation of taking the weight (in kilograms) and dividing this with a value obtained by squaring their height (in meters). For example, an individual whose height is 1.60 meters and weight is 70kg, will have a BMI of 70 divided by (1.60 x 1.60). The BMI therefore would be 27.3.
At present, a person is classified as overweight when the BMI is ≥ 25kg/m2 and obese when the BMI is ≥ 30kg/m2. This is further classified into moderate obesity ≥ 30; severe obesity ≥ 35 and morbid obesity ≥ 40. The recommended BMI range is between 18.5 and 24.9 kg/m2.
The relationship between weight and fertility is REAL!
In obese women, spontaneous conception is often delayed. In fact, studies have shown that the probability of pregnancy is reduced by 5% for every unit of BMI that exceeds 29kg/m2.
We now know that obesity affects the chances of natural pregnancy by interfering with several hormonal and metabolic mechanisms. Female obesity, especially in women with high abdominal fat distribution have lower frequency of ovulation and reduced chances of pregnancy and interestingly, this is also true in obese women who do ovulate.
There is also a strong relationship between obesity, Polycystic Ovarian Syndrome (PCOS) and insulin resistance. Women with a raise BMI have a threefold greater risk of infertility.
This negative effect of obesity on conception is also clearly seen in patients that undergo assisted conception treatment. Although the medical evidence may sometimes appear contradictory, the general thrust of the evidence is that when compared to women of the recommended BMI, women who are overweight or obese require a higher dose of stimulation medication, have a lower chance of getting pregnant (reduced by approximately 30%) and have an increased miscarriage rate (increased by approximately 30%). That said, the exact mechanism that cause these negative effects are still unclear. It is important to note that the detrimental effect of excess weight applies for both overweight as well as obese women.
Put simply, you don’t have to be very far off your ideal BMI to impact on your fertility!
The good news is that the negative effects of excessive weight on fertility appear to be reversible. This has been well demonstrated in women with PCOS where weight loss of even 5kg has been associated with improved hormonal levels and improved reproductive function.
Yes – its reversible!!
In males, the effect of obesity on fertility have been less studied but it remains clear that obesity leads to lower testosterone levels and also other endocrine abnormalities, higher scrotal temperature and higher rates of erectile problems. While many studies have shown an increased likelihood of abnormal sperm parameters among overweight men and and risk for subfertility among couples in which the male partner is obese, other studies have failed to show this association.
Therefore, in conclusion, based on the available evidence, it would seem sensible that all women and possibly their partners who intend to conceive maintain a healthy weight, which is aiming for a BMI between 20 and 25kg/m2. Similarly, women who are about to embark on fertility treatment should optimize their body weight, as weight loss would incur a positive reproductive effect on many important outcomes of fertility treatment and this effect should not be underestimated.
Coming up next …… how do we do this?