People are always determined to criticise you, in all sorts of spheres of life it seems. I have a horse and I am trying to keep him without shoes as it's more natural for a start (horses aren't born with metal shoes on their feet) and also he's been ill and his feet aren't strong enough for metal shoes yet. But the amount of stick and abuse I get from some people (not everyone) has been unbelieveable. Luckily my vet is supportive and I just tell them that the vet says he's not allowed to be shod - which is true. (Although even when the vet says he's able to be shod, I'm not going to!)
I've got tougher though, if anyone starts on at me I just tell them that it's under the vet's control and they can speak to the vet if they like and they tend to shut up then. In the future when he is better and still not shod I shall tell them he doesn't need shoes.
So I feel like I am well trained to prepare for people asking me about the diet. Firstly I don't criticise what they eat so why it is any of their business what I eat. Secondly that I do have the support of my doctor and I can provide them with lots of information and studies relating to the diet if they like. Hopefully that will shut them up.
Yes it's nice that people are concerned, but once they've had it explained to them they should leave us alone!
I've told my housemate and 2 friends that I'm doing the Cambridge diet, not even my Mum. Not because I am ashamed but because it's really not anyone's business.
So yes, I say either lie, or just tell them you are healthy and being monitored regularly and whilst you appreciate their advice it is your body and you'd thank them kindly to stop bringing the subject up.