I am 20 years old female..bt my weight is just 41 kg..and height is 166 cm...how can i improve my weight quickly?

Slow and steady: Energy in = energy out. So if too much energy is going in e.G eating more food than your body is capable of metabolizing including exercising you will gain weight. I tell my patients to work with a 500 calorie deficit per day. Here are some scenarios. You eat 500 calories less per day. Or you eat 250 calories less per day and exercise 250 calories more. 500 x 7 =3, 500 calories = 1 pound loss.