I grew up in an abusive home. I know what you're feeling. The others on this thread mean well, but they have no idea how much worse your situation could get if you try to call for help.
If your parents left marks on you, take pictures. I hope you have a camera or ipod or something that can take photos since they took your phone away. Maybe a webcam on your computer? But take pictures before the marks fade. Show the pictures to a friend first and have them go with you when you tell a trusted non-family adult.
Comply until you can get help. I know, it sounds like a nightmare. It's the only way for you to stay safe. You have to act like you're magically cured because they will keep up this behavior even after they see it isn't helping you. Because they don't care about helping you, they only care about themselves. So comply. Eat what they give you, or employ your best tricks to make it look like you are.
Unless your parents are weighing you naked (which is seriously messed up and I hope they are not), you can trick the scale with your clothing. Try to weigh after your shower so your hair is wet. Wear something bulky. Carry heavy things in your pockets or sew weights into the hem.
I technically shouldn't do this, but I work with teenagers and I'm earning my social work license. I have connections. Message me if you need help finding support in your area. You are not alone.