According to WHO, overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health, as well as infertility. Obesity indicator for an Asian adult can be measured by two methods as follows:
1. Body Mass Index (BMI) is calculated as weight (in kilograms) divided by height (in meters) squared (kg/m).
2. Waist to Height Ratio (WHtR) is calculated by waist size (in centimeters) divided by height (in centimeters). The proper ratio is 0.5. Ratio bigger than 0.5 basically means overweight
There are several researches from different institutes studying the relation between body weight and the quality of sperms as follows:
Sperm concentration: Fat tissues accumulated around testicles causes higher temperature, adversely affecting sperm production. Increased fat induces conversion of male’s testosterone into female’s estrogen, which lowers semen production in process. This could lead to insufficient semen for natural reproduction and intra-uterine insemination (IUI).
Sperm motility: Lowered male’s testosterone leads to incomplete growth of sperm’s tail and causes non-progressive sperm motility such as swimming in loop or backward. This decreases the chance of fertilization as sperms may not survive the pH in vagina.
Sperm morphology: Defective sperm production causes sperm deformities. Common deformities are found in the head. Neck and tail deformities are also found. These deformities, no matter how, lead to infertility as the eggs will reject deformed sperms, thus fertilization and implantation will not happen. More unfortunately, this could cause defective embryos.
Sperm DNA: Oxidation stress condition is usually found in overweight people due to more oxidant present in the body. These oxidants are harmful to the genes in DNA, damaging Chromatin thus causing miscarriage or congenital anomalies. These errors in DNA can also be carried on to later generations
Written by
Dr.Sirisuk Ouitrakul
Obstetrician and Gynecologist, Reproductive Medicine