How to gain weight loss

Do you have a problem about overweight? if you have the problem,have you ever try to gain weight loss? if you ever tried to do.can you tell us how to gain weight loss.It is not easy,isn't it.it depend you your eating habit,your metabolism  in your body,the structure of each person's body,exercise and what you prefer to do each day.someone feed many food a lot,after that nothing to do.just sit then sleep and lack of exercise.Some eat food a bit and go to exercise everyday,but they eat all meal and each meal they eat a lot.they also have never gain weight loss.do you ever notice someone who eat a lot,but their weight has never getting increased,on the other way someone eat a little bit and also go exercise,but they  have never gained weight loss.The answer is it depend on each person's metabolism that is influenced by genetics.