>Men today have 50% lower sperm count compared to 1970. Sperm count/testosterone level is strongly correlated with body weight; if you account for how much fat

>Men today have 50% lower sperm count compared to 1970. Sperm count/testosterone level is strongly correlated with body weight; if you account for how much fatter people are nowadays the reduction is much less (e.g. compare a healthy weight person from 1970 to now). Similarly a lot of the reduction in fertility is explained by people nowadays being fatter.