As they say, there are two rules in improv: Never say no, and never ask why. When another actor asks 'Why?' or says no to something you're suggesting, then it's very clear that they're putting the onus on you, because they're not comfortable with it themselves.
“I like looking nice, but I always put comfort over fashion. I don't find thin girls attractive; be happy and healthy. I've never had a problem with the way I look. I'd rather have lunch with my friends than go to a gym.”
“Facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty.”