For generations, the bathroom scale and its derivative—the body mass index—have served as medicine's shorthand for metabolic risk, including reproductive health. A large Danish study now quietly dismantles that assumption, finding that body fat percentage is a more truthful witness to a man's fertility than his weight-to-height ratio alone. Among over a thousand young men, those carrying excess fat showed sperm counts nearly a quarter lower than their leaner peers, even when the scale declared them normal. The finding invites a reckoning with how easily a single number can obscure what the bod