I've been overweight myself, all my life in fact. It really hit me when I got up in the scale and I saw 3 digits. I was weighting over 110 kg so I though i had to do something and after 5 years here I am. I weight 69 ish kg and I'm somewhat fit...
The best and quickest way to lose weight is exercising and learning how to eat healthy. A nutritionist might be advised to help you draw your food plan. Most gyms nowadays offer that for free (at least in my country).
I believe that if.you prove those ppl that you can get in shape, not only you will feel better about yourself they will also stop picking on you... hopefully! Hope I was of any help 😅