is this okay for my parents to do this

She doesn't want you to have health problems. Is there some reason why you're resistant to becoming a healthier weight? It sounds as though your whole family could do with supporting each other and all of you could lose weight together.

As you say, your mum is probably doing this because she cares about you. I know this is perhaps childish of me, but if telling her that her comments upset you hasn't helped, I think I would be inclined to start commenting back about her own habits/weight, and perhaps suggesting that both of you could work on improving your diet?

Well a simple way you could bring it up more seriously, is by sitting down at the kitchen table or living room with both of your parents and having a serious conversation with them both about this situation. What you have written in this thread could be something you tell them, use things you said here, and explain how it makes you feel.

I'm not totally sure if this will be helpful, but I hope it will at least get you thinking of ways you could talk to your mother and maybe even your father about this. I know that getting comments like that is hard, with my parents they would skinny and fat shame me, so conversations never ended well, I hope this will be different for you if you decide to speak to them, stay safe, please.

Your folks are indeed looking out for your best interests. Your figure can mean the difference between date or no date. Engagement ring or no ring. Successful, honest, clean, handsome & educated husband. House on a hill, nice cars, health-care, quality food, annual vacations, kids in private schools and savings (planning) for retirement future.
OR ... You can eat yourself out of the market, settle for the alcoholic trash-truck guy enjoying life amongst fighting neighbors and police living in a seedy trailer park.
Here's a Hint: Your body is a window into the inner condition of your soul. Maybe Mom realizes that with herself.

Your folks are indeed looking out for your best interests. Your figure can mean the difference between date or no date. Engagement ring or no ring. Successful, honest, clean, handsome & educated husband. House on a hill, nice cars, health-care, quality food, annual vacations, kids in private schools and savings (planning) for retirement future.
OR ... You can eat yourself out of the market, settle for the alcoholic trash-truck guy enjoying life amongst fighting neighbors and police living in a seedy trailer park.
Here's a Hint: Your body is a window into the inner condition of your soul. Maybe Mom realizes that with herself.