某些人群比另外一些人要胖一些,这是纯属偶然
1.happen to 偶然,碰巧
happen to do sth.= do sth.by chance= do sth.by accident
sb.happen to do sth./ happen to be adj.
2.另外,happen to 也有发生之意思,
sth.happen to sb.某事发生在某人身上