A man's weight affects his sperm's genetic makeup and could lead to a predisposition to obesity in his children, according to a Danish study published in the journal Cell Metabolism.
A five-year study undertaken by Dr Romain Barres of the University of Copenhagen has revealed that the sperm of thin and obese men have different genetic markers, which could change gene behavior in the body.
Dr Romain Barres believes it is wrong for health advice (not to drink alcohol, to stay away from pollutants, to eat a balanced diet, etc.) to be exclusively targeted at women during pregnancy.
He asserts it is also important for men to adopt a healthy lifestyle before a child is conceived.
To come to this conclusion, the researchers tested the sperm of six obese men who were undergoing bariatric surgery to reduce the volume of their stomach.
Sperm samples were taken before the procedure, one week after it, and for a third time a year later.
The findings showed that the men's sperm had undergone significant changes a week after the operation and a year later. Different genetic markers were observed, which could change the way genes express themselves in the body.
Their findings were the same when they compared 13 slender men who had a Body Mass Index of less than 30 with 10 moderately obese men.
No scientific study has explained how these changes occur. However, the researchers found a link between these genetic changes and the genes which control the appetite and the brain.
In other words, a man's weight can influence the health of his children, in particular whether they have a predisposition to obesity.
Dr Barres said "Until we know more, would-be parents should just aim to be as healthy as possible at the time of conception and not be drawn to faddy diets or other activities in order to try and influence the health of their children in ways we don't properly understand."
To undertake further research into this change in the sperm's genetic makeup, his lab is now working with a fertility clinic to study the genetic differences in embryos (that must be discarded and can be used in research after 5 years, under Danish law) resulting from the sperm of men of different weight.
Once the researchers have accumulated a large number of participants, they will be able to issue new comparative data after studying the cord blood of the children that each of the men fathered.