You should be asking the health section of Yahoo Answers...but I can give you some advice.
Don't do it and stop what you are doing to your body right now.
I was a model, went to casting calls, the works...when I was younger. I regret it deeply and will never return to it. I won't model today because the industry (as most models who have been in the business a long time will tell you) has lost its mind and doesn't care for the girls anymore. They don't care if you live or die, as long as you make a pretty corpse....pretty bad, don't you think? But it is true. They don't care what you do to get yourself looking like a skeleton...they do not care for your health at all...especially the most elite fashion houses and companies.
You are also very young. Your parents will be in control of any money or jobs so, whether you like it or not, they will have final say. I am hoping your family sees things more realistically than you do. Also, Victoria's Secret does not hire child models. The girls they use are in their 20's and up depending on how they look. They might take you at 18 but it all depends on if you have a look they are interested in. In other words...you can train properly all you want to, but you have no say and no way to work for the company you choose to work for. Each company looks for something different; You are just a number, a pretty face, a different look they want....nothing more.
Stay in school, act your age, enjoy your innocence and your life. Appreciate what you have. Have some self respect and love the way you look right now. Do not go on a diet or an exercise regime unless your doctor tells you to....and get a second opinion before you actually go through with it.
Modeling isn't like you see on TV...it's not America's Top Model. School first....then talk to real models and find out if it's somethign you would like to pursue and acquire an agent.