Oh, so you are talking about change of the species without evolution?

We're talking about giving time for harmful effects to manifest themselves. If you are going to eat a diet which does not resemble what the human body evolved to deal with, then at least follow something that resembles what has been available to your kin for countless generations. If you start consuming brand new diets (not just in terms of the substances and nutrients they contain, but the concentration and dosage and regularity) you're much more exposed to potential harm.

But we are doing a brand new diet. About 2000-10000 years ago human diet consisted of around 80% animal flesh.

Citation?

Besides, when I said brand new I meant things which have emerged in the last 150 years, especially highly processed foods.