All of my male Sims are overweight (Sims 4)

I've recently noticed that all male babies born become overweight as they grow up. I don't mean a gradual process; as soon as they've aged to a child they're automatically chubby. The first few times I assumed it was because the mother had become overweight from previous pregnancies. With another family I guessed it was because the mother was slightly curvier. This time though the couple were both fairly skinny and when you go to full edit mode and show possibly child genetics none of them come up as overweight. This also never applies to the girls, just the boys. Obviously I don't mind my Sims being overweight but it's obvious that there is some sort of bug in my game rather than this being due to poor diet or other factors that are always blamed for it. Could someone please help?