Gillian McKeith
Biography
What can we say about Gillian McKeith that isn't potentially defamatory? Well, she was born in September 1959 in Perth, Scotland, and wrote a number of books on the subject of nutrition. This led to the television series You Are What You Eat (2004-7 on Channel 4, with a more civilised version airing on Channel 5 in 2022), where she changed people's diets by shouting at them and pointing at their faeces. A competitive version of this format was made in 2007. It emerged around this time that McKeith was not a qualified medical practitioner and that her Ph.D. was not from a recognised academic institution; as a result of these revelations, she ceased to describe herself as "Dr. McKeith", because she is not a doctor.
Web links
Wikipedia entry on Gillian McKeith debunking everything she stands for. And that's from a neutral point of view!