I refuse to congratulate anyone on losing weight. I will congratulate you on a pretty outfit, a pretty haircut, a confident poise, a happy demeanor, an academic or professional accomplishment. I will not congratulate you on being thinner.
If you are eating a more balanced nutritious diet, if you are exercising more regularly, i applaud that. But if you have been starving yourself through volition or illness, i do not want to applaud that.
I do not think the government should interfere in your right to harm yourself (one of the things that makes me a Bad Liberal) but damned if i as a person am going to encourage you to harm yourself.