Give you a plan from several dimensions, but remind you that any good slimming plan needs perseverance, otherwise, it is all empty talk.
Diet: Eat two meals a day, have a full breakfast (before 9 o'clock), have a good lunch (I suggest eating at 3 o'clock in the afternoon, otherwise you will be very hungry at night), and don't eat dinner. If you are too hungry, eat some fruits, such as watermelons, tomatoes, cucumbers and apples, instead of bananas. Fat and high-fat foods, mainly crude fiber foods or vegetables, are prohibited for breakfast and lunch.
Exercise: Run for at least 50 minutes every morning and evening and at least four days a week. Remember, jogging is enough, you don't have to compete with others. Even if you only walk twice as fast, as long as you keep running for 50 minutes, you will burn fat.
It is difficult to persist in running at the beginning, because vital capacity and leg muscles are not easy to persist, so you can use one week as the adaptation period, and you must run for more than 50 minutes every time after one week.
As long as you follow the above methods and combine your current physical condition, you can ensure that you can lose 10 kg to 20 kg during a holiday, and it is not easy to rebound. If you can persevere, make sure you have a good figure.
In addition: special reminder, because you are a middle school student, you are strongly opposed to taking any diet pills, which may cause harm to your body and outweigh the benefits.
The last sentence: keep your mouth shut, don't be greedy, exercise more and stick to it.