One other theory put forward by Tim Noakes is that the US dietary guidelines that was introduced in 1977 which recommended to eat lots of carbohydrates is respo

One other theory put forward by Tim Noakes is that the US dietary guidelines that was introduced in 1977 which recommended to eat lots of carbohydrates is responsible for the huge increase in obesity and mental illnesses that exploded in the 80s. A high carbohydrate diet was never scientifically proven or tested. One guy (Ancel Keys) had a theory, cherry picked some countries that showed a very small correlation. But political things were afoot in America and Nixon went with his plan and enacted the US diet regulations in 1977 that promoted grains which helped US farmers especially the corn industry. The other countries soon adopted it since US leads the way. But if you look at the graph of when diseases like obesity, mental illness, depression, heart disease really explodes from 1980s, right when the dietary guidelines are taken up. Of course correlation doesn't equal causation (which is one of the flaws in the Ancel study). But it's definitely something we should do studies on.