So, weight loss is a sensitive subject.
A coworker or friend may offer you a treat and you want to politely refuse it.
May I suggest...
Do NOT say, "No thank you, I'm on a diet."
Because people choose to be offended by this.
It implicates that maybe THEY should be saying "No" to the goodies as well and we never want to assume anyone is unhappy with their current state of health or act "holier than thou." Not only is that offensive, but it makes people want to sabotage you. And they will. And they might succeed.
"No, I couldn't possibly eat another thing.. I'm full."
Or, "Thanks, I'm not hungry.. maybe later."
What are some of your suggestions?