The term obesity was coined in the middle of the 20th century as a concerted e
ffort by medical doctors 「to say」: this is a medical issue, one over which w
e have authority and expertise.
第三行，括號是我加上去的，有大大可以提供這樣用法的例句嗎？

This reply is my attempt to say: don't sweat over grammatical details all the time, have fun imitating what you read/hear and you'll be fluent soon.