Kind of following on from OlsBean's post really - but this might be of interest to some here. bbc.co.uk/news/magazine-296...
I must admit that I do from time to time think about the idea of us being modern men and women in cave-dwellers' bodies and a lot of what we eat plenty of (or do I mean only too much of?) nowadays just wasn't available to people in the era that our bodies have evolved to. E.g. cakes, pies, sugar (i.e. sugarcane / sugar beet products), chocolate, carbonated drinks, etc., etc.
Of course, our cave-dwelling ancestors did consume sugars, but that would mainly have been through the fruits and berries they foraged and from honey (if lucky enough to be able to get at that). And they would have eaten animal fats - though that would have been periodically rather than frequently, i.e., when the hunters of the group returned with an appropriate catch.