That's no good. But the way i see it, it seems he just doesn't quite understand your reasoning. I don't think he's trying to sabotage you deliberately, he's trying to stop you hurting yourself (it seems that's what he thinks you're doing). Maybe sit down with him, thank him for being concerned and so thoughtful and explain about the diet and how it works and that it's not anorexia. if I'm not mistaken, this diet is also short term? in which case make sure he knows that.
35kg lost. (November 2005 - October 2006)
15kg gained again (as at October 2010).
Back to the drawing board - Let's do this thing!
"You can't change the winds, but you can change the sails"
"Reach out and take control of what lands in your lap"