My favourite one relevant to my own research is that women who are overweight when they are younger (premenopausal) are less likely to get breast cancer than those who are underweight. But when they get older, women who are overweight are more likely to get cancer than those who are underweight. The two situations swap over. This is to do with the hormones within the fat, and the type of breast cancers women get. But i think it’s a good fact because it’s the only cancer I know of where it serves to protect people from cancer.