While the program is very interesting in that it shows people the error of their ways in eating a diet consisting of burgers and crisps, you need to take Gillian McKieths advice with a pinch of salt (pardon the pun).
Apparently, she has a slightly iffy doctorate - if you believe the article at http://www.quackwatch.org/04ConsumerEducation/Nonrecorg/clayton.html. The same college has churned out people who have spouted such rubbish as:
"all cancers, AIDS, and many other diseases are caused by "parasites, toxins, and pollutants" and that they can be cured with herbs and a low-voltage electrical device, sometimes within hours"
"health and weight control depend primarily on proper balance between an alkaline and acid environment that can be optimised by eating certain foods"