Hi Trang! You asked me how to stay in shape and live healthily because you are put on weight. Today I will answer. 

Firstly, you should eat enough meals and calories. You need many nutritions: vitamins, protein, mineral,... You should eat: vegetables, fish,... and add some fruits. You should eat less unhealthy food, such as: junk food, fast food,...  instead of eating some bread and drinking a glass of milk for your breakfast. 

Secondly,  you should play less computer, smartphone,... and watch less television. You won't feel tired and weak. 

Thirdly, you should play sports and games. Such as: badminton, swimming, football, hide-and-seek,... You will feel more stronger and full of energy after playing it. 

Lastly, you should smile more everyday. Many people said:" A smile squats 10 tonic scales". The more you smile, the longer you will live. 

They are my advices to live healthily. Please reply if you stay in stay in shape successful.