A disclaimer doesn't remove the damaging edge to your words.
I'd appreciate a "look, Tony, we're friends, so I feel like I can tell you this without expecting long-term and irreparable damage to our friendship, but despite what your goal weight is, you don't fit into that outfit, and I can't be seen with you if you continue to wear it." Okay, so it's offensive, but it's the truth and I have to deal with it.
Leading with "No offense, but..." makes me hate you. More than I already do.
See also "bless his heart..." For example, "aw, that dude is the grimiest douchebag in the world, bless his heart!"
