Nothing that I've actually seen with regards to Medieval diet is as certain or unqualified as what the BBC News article proposes. Each point following a "maybe" or a "perhaps" should be taken with a huge grain of (relatively inexpensive) salt IMO. I suppose news fluff pieces are not designed to be analyzed in detail, but I think the goal of the thing is to make modern people feel uneasy about how lazy they are and how much sugar they eat. The reference of a television show from the get-go was probably a clue as to the intended audience.