He's a crank , trying to make money . Just because he's a doctor doesn't mean he's speaking for all of them
If this diet was safe the NHS would be all over it like a rash , just a quick Google will pull up lots of controversy
If you are an athlete or need to lose weight for an operation then this sort of diet may be helpful if it's monitored by a health professional but this sort of diet plan is being thrown around by the likes of you as something the general public can take up . It's clearly a highly restrictive crash diet .
You may have the motivation to put yourself through this sort of thing but its dodgy and most people will fail