Hrm.
No, it's not right to make negative comments on a person's weight regardless of their size. I think that's the difference between what your co-workers are saying to you, and what co-workers are saying to others who like the comments.
When a co-worker says "Wow! You're losing weight!!!" and it's a positive thing, then you take it that way and feel better about yourself. When they say "Eat a cheeseburger!" what they're really saying is they don't approve and it is a negative comment, and it makes you feel worse.
If someone were to say "You're looking nice!" you may have a different opinion on the matter of co-workers' opinions, but unfortunately they aren't saying positive things. And most certainly negative comments are rude. You should tell them so... politely

....that people come in all shapes & sizes, and regardless of how
they feel about your shape and size, it's not polite to make such negative comments about you not being large enough. You certainly would never speak to someone about them not looking good enough in any way shape or form, so you don't like hearing the same about yourself.
However, saying that they don't have the right to be jealous is a little off the mark. Everyone has the right to be jealous. Everyone has the right to feel any emotion that they feel. (And maybe they
have tried as hard as you have worked. We don't want to judge others even when they judge us.) It's how they deal with it that matters. And again, they are not dealing with it well by making negative comments about you in order to feel better about themselves.
So, stand up for yourself, let it be known, but then get back to being your regular friendly self at work and hopefully the others will realize that you just want to go about your day the same as they do.