haha, my husband believes the same thing. I've never told him that I fully intend to Water Fast for several weeks while he's gone! I'm easing him into the understanding of this stuff. He used to freak out but now he's seen me do a "cleanse" (not a fast, right?) that was really a juice fast of 14 days. I recently told him that I fast 1 day weekly. I'm slowly easing him into the world of fasting so he won't freak out about my life being in danger. When he comes back, I'll likely tell him how long my Water Fast was and the results and that I intend to do 10 days regularly.
I think it's how our culture sees eating - the people that think you will die just have that impression but no special knowledge of fasting. Keep that in mind. You can ask where they're getting their information from and find that it's just a culturally ingrained assumption. Some may believe it's healthier to eat McDonalds than to fast, don'tcha know!!! ;-)