Hello dear,
Firstly, the built and personality of a person is genetically determined and can be influenced by factors like diet, exercise,
hormonal balance in the body, etc.
Secondly, the weight gain products are only dietary supplements & should not compromise on routine healthy food such as:
1. Consume more of natural diet like fresh fruits, green vegetables, milk, eggs, wheat, etc.
2. Avoid oily and junk food.
3. Stay away from
smoking & alcohol.
You can consult a dietician and get a diet chart regarding the need of calories in your body based on your height and weight.
One more thing...do not try to gain weight all of a sudden under the influence of medications. It is a gradual process & may take time.
Under such conditions, intake of medications or weight gain supplements without proper guidance may have harmful effects on the body.
Wish you a healthy life.
Take care.