Being overweight does not slow down a man's sperm, suggests an investigation.
A new study contradicts the theory that having a high BMI reduces male fertility.
After analyzing more than 200 men with healthy, overweight and obese BMI for 10 months, Nigerian scientists found no significant differences in the speed, size or shape of their sperm.
This occurs weeks after the Bath and North East Somerset clinical commissioning group announced that they will deny IVF to women if they have a male partner with a BMI greater than 30, who is classified as obese.
The official guide from the National Institute of Excellence in Health and Care (NICE) also states that men with a BMI greater than 30 are less likely to have children.
Overweight does not slow down a man's sperm, suggests new research (stock)
The researchers, from the University of Benin, analyzed 206 healthy men whose BMI varied from normal, from 18.5 to 25, to obese.
The men, who were between 20 and 40 years old, presented sperm samples that were evaluated in a laboratory for their counting, motility and shape, as well as for any anomaly.
They were followed for 10 months.
According to the researchers, the results, published in the International Journal of Reproductive Biomedicine, suggest that "high BMI does not significantly influence the quality of semen."
DOES INFERTILITY AFFECT THE RISK OF PROSTATE CANCER OF MEN?
Infertile men are more likely to develop early-onset aggressive prostate cancer, research published in July 2018 suggests.
Those who can not have children naturally or via IVF are generally 47% more likely to develop the life-threatening condition, while men younger than 50 have triple the risk, a study found.
Undiagnosed prostate tumors can lead to infertility, while low testosterone levels could lead to the development of both conditions, the researchers said.
Early-onset prostate cancer affects approximately one in every 1,000 parents under the age of 50.
About 35 percent of men have poor fertility, while two percent can not have children.
The researchers, from the University of Lund, analyzed all parents and their firstborns in Sweden between 1994 and 2014.
The information was taken from birth, cancer and assisted reproduction records.
Parents who underwent intracytoplasmic sperm injections (ICSI) were compared against those who became parents naturally or via IVF.
ICSI involves doctors injecting a single sperm into an egg. This is different from IVF, which mixes the sperm with the eggs and allows them to fertilize.
It usually costs up to £ 1,000, in addition to FIV rates, and is recommended for men with very low sperm counts or who have had difficulty having children.
The results suggest that men who have ICSI have a significantly higher risk of early-onset prostate cancer, but not late.
IVF does not influence the risk of men of any type of disease.
ICSI itself does not increase the likelihood of men developing prostate cancer, however, infertile men may opt for treatment in a last attempt to become parents.
The principal investigator, Dr. James Osaikhuwuomwan said: "The comparison of the semen parameters of the study population with BMI showed that there were no statistically significant differences in semen parameters (sperm count, motility and morphology) of the study population with normal and elevated BMI.
"In addition, a comparison of semen defects among the BMI groups of the study population noted that there was no statistically significant difference in semen abnormalities among men with normal and elevated BMI."
Although a link between a man's weight and his fertility is not found, the alembic of Osaikhuwuomwan recommends that males maintain a healthy size to benefit their general well-being.
He said: "There is no controversy that overweight and obesity have become major health concerns around the world and the benefits of weight control can not be over emphasized.
"Male partners of infertile couples with a high BMI who seek treatment can be sure that their BMI will not adversely affect the quality of their semen or their search for conception, but general obesity is discouraged for a healthy life."
Speaking of the findings, Hana Visnova, medical director of the fertility clinic IVF Cube, Prague, who was not involved in the study, said: "Actually there is very little evidence to link obesity with the quality of sperm in men and this justifies a deeper study.
"However, there are other things to consider when it comes to libido and sexual desire.
"A high level of obesity indirectly influences sexual appetite, obese patients may have high blood pressure and other health problems that can cause erectile dysfunction and libido deterioration."
Dr. Allan Pacey, a fertility expert at the University of Sheffield, also recently argued that "there is no consensus" on the evidence suggesting that male infertility is driven by a man's BMI.
These notions contradict a study published in July last year that suggested that the sperm count in the West decreased by 60 percent in the last 40 years, and the researchers blamed obesity, as well as stress and smoking.
Other research published last September by Indian scientists also suggested a link between obesity and men who have lower sperm quality.
Dr. Gottumukkala Ramaraju, lead scientist, said: "The health and reproductive performance of sperm in obese men are more likely to be compromised both qualitatively and quantitatively."