I think the correct answer is: The author include details about the changes in diets over time to inform readers about how sugar has transformed what we eat.
The first clue that leads us to this answer is the title, Sugar Changed the World, we can infer that the author is going to tell us the changes sugar has produced throughout history, that includes the diets. The title also makes us think that the text is going to be informative as the writer describes events related to sugar, giving statistics and facts. A persuasive tone is not detected yet, so we as readers are not expected to make a change in our beliefs, answer 1 and 4 are therefore incorrect.
Although some statistics are shown, this kind of texts are not mean to entertain readers with "surprising statistics" as it has an academic tone and is probably extracted from a book or research paper, which primcipal objetctive is to inform. If the statistics were used to amaze us a more colloquial language would be used and it would be part of an entertainment magazine.