First of all, if you sit at school for a long time, your thighs will thicken and your waist will have fat. You are still young, so you should slim down and keep in shape while you are young. Because it is not easy to lose weight when you grow up. So, go out for a walk 10 minutes between classes, and don't sit in your seat all the time. Losing weight is not a day or two. Throughout the history of the earth, those fat people all over the world have the same problem, that is, they can't control their mouths. Eat too much greasy, high-calorie and high-fat food. It is easy to lose weight and control your appetite. Too forgetful in front of delicious food. Eat less snacks, eat less meat and eat more vegetables every meal, and it will be ok if you are full at 7 pm. Talk more and eat some fruit at ordinary times. If you want a perfect figure, you can add some exercise programs.