There has been great concern, as far as that is now possible, about a study claiming that a fast food diet can irreversibility destroy the capacity of males to produce sperm, killing off sperm producing cells with things going down by the age of 18years:
https://www.telegraph.co.uk/news/2019/06/24/mens-fertility-irreversibly-damaged-age-18-thanks-western-junk/
There is no link to the actual study, which apparently was a conference paper that has not yet appeared. Thus, questions such as whether obesity and fat consumption, and vitamin and mineral intake may not have been addressed, but probably the death of the sperm producing cells may have been due to the fact that junk food is ultra-poor nutrition anyway. There was material published in the previous news cycle about a junk foods diet causing shrinking of the brain:
https://www.deakin.edu.au/about-deakin/media-releases/articles/does-junk-food-shrink-your-brain
Thus, the sperm destruction is not unsurprising. The youth of the West are literally eating themselves and their genetic future, to death.