I am a junior 1 student, weighing 77 kg. Believe it or not, I've always wanted to gain weight, but I just can't. Maybe it's natural, but I will give you some advice:
I get up at 6:30 every day, start eating at about 6:45-6:55, finish eating in 5- 10 minutes, run to school at about 7: 15, and then play the second landlord with my classmates. Classes begin at 7:30, 7:45-7:50. Sometimes it takes 2-3 minutes (fried rice with eggs, eating too fast), and then go down to play football immediately after eating. Hehe, I just can't get appendicitis or anything. The man of god will play until 12:40, and study by himself in the afternoon. Then 1:30 will start the class, and the school will end at 3:05, and the teacher will play until 4:00.
Maybe it's a habit. ....