This suggestion may help some people. In the long run. Unfortunately, George Monbiot who wrote the article says he has had the greatest difficulty understanding some of the research so I reckon most of us will have to take it on trust for the time being.
My worry would be that, whilst the suggested cause could well be applicable in some cases, or at least be a contributory factor, one can see how all people with dementia might be branded as consumers of junk food. Blaming the victim is all too common in matters of health, particularly where the media are concerned.