Fad diets are a 'big risk,' Paul McKenna warns The TV hypnotist Paul McKenna has warned people against using fad diets to lose weight. The self-help guru claims that diets rarely work and that obesity is primarily caused by "emotional eating." Speaking with BBC Radio 5 live's Phil Williams, McKenna said: "It's a very big risk to take." They're treating the symptom. They're saying starve yourself - and you'll lose the weight. I'm saying, what drove you to put on the weight in the first place?