If you're asking genuinely, yes it can be condescending to persist in asking for 'exactly' what they've done, especially when the discussion isn't focused on their diet or their success and failure.

People tend to not want advice when they're not seeking it, and when someone wants to dissect every detail of what they've done that hasn't worked, when they mentioned it merely as an anecdote, it tends to be perceived as condescending.

I'll keep on asking exact things you've done as long as you keep claiming something doesn't work, when I know it does and have worked for many.

About advise part, I am not looking to offer him any advise I am simply defending the method and ideas, so that other people can find success with it similar to what I've done for me and for many others.