Obesity, high (BMI between 30 to 35) or very high body mass index (BMI >35), is associated with impairments of sperm quality, notably a decrease in seminal sperm DNA integrity and sperm motility.
The negative impact of male obesity on sperm DNA integrity could lead to serious consequences for fertility. Indeed, sperm DNA alteration has been linked to impaired fertilization, altered embryo development, lower implantation rates and a higher incidence of miscarriage. Moreover, a recent link between high paternal BMI and decreased live birth outcomes after assisted reproduction treatment has been highlighted, possibly due to reduced embryo development, reduced implantation rates and higher pregnancy loss.
Although the underlining reasons are not well known, oxidative stress may be the key mechanism linking overweight or obesity with male infertility by inducing increased sperm DNA damage. Indeed, BMI and abdominal obesity have been correlated to systemic oxidative stress assessed in plasma and urine. In addition, the testicular microenvironment is also exposed to oxidative stress and a positive correlation between BMI and seminal oxidative stress has been observed.
It is recommended to reduce body weight to reach a BMI below 30, for males trying to conceive, and to take nutritional supplements which protect against oxidative stress.