Respuesta :
the sentence that contains the main idea is that "chocolate has been found to be a cause of weight gain."
the paragraph is pointing out the fact that it has been found to cause weight gain but the paragraph goes on to say that some of the researchers don't dive deep enough.
i hope that was helpful :D
"Chocolate has been found to be a cause of weight gain" OR! "But chocolate does have some health benefits" <-- this one most likely because the rest is about healthy stuff i dont know lol good luck! <3