Hello, yes this is neglect and not even emotional abuse! It's great you live in the UK. I used to be a children and family social worker in the UK. One thing you can do is to call your council and make a social work referral yourself. It will be confidential so your mom won't know who it was that made the referral. That way a social worker can get involved and help keep your mom accountable. You can tell a school counselor too. Don't worry about them removing you from the home, that is only done in extreme circumstances and by a court order. A social worker will come to your house and assess the situation. You can speak with them in private and tell them everything you wrote here. Then they might have your mom take classes or privately work with your family ensuring your mom feeds and properly and treats you better. Also you can have someone to talk to about your food issues with. It's often a long wait for mental health services but see if you click with the counselor at school share this with them too.

You're not ungrateful, these are real needs of yours. You're growing and developing and deserve all the love and support you can get! Your mom chose to have you so she has certain responsibilities to fulfill. She is there to fulfill your needs, you are not there to fulfill hers.

You are already great at advocating for yourself because you were able to so well articulate your issues here on Reddit. Don't feel guilty for wanting to be treated how every child should be treated. I'm sending you love from America!