The "picture" doesn't seem accurate. If they were feasting so much, then why didn't they go obese?
Without those two it's a bit difficult to get to the point of obesity in a world where you have to walk a lot because cars and elevators don't exist.
That leaves vegetable oils, and cars. I think it's like 70/30 personally.
I imagine they did have a fair amount of obesity in the older members of the population, although it's also possible that the sportier ones (which I'm guess would have entailed things like polo and horseback riding) would remain fit into old age.
Also, food unevenly distributed across the day. Any one individual probably wouldn't have a large breakfast and elevenses and a large lunch and afternoon tea and a large dinner, on every single day. Even if you can find examples of each of those separately.