Apetamin contains cyproheptdine which is used to increase appetite in case of chronic illness. It will help to increase appetite but it used for short term only. If you want to gain weight then gradual and natural process of weight gain is advisable. There are various causes of underweight like inadequate food intake, prolonged meal time gaps, and increased physical activity weight increasing food intake. Other reasons are mostly medical conditions like TB, cancer, malabsorption, hyperthyroidism, and anorexia nervosa etc. Natural ways of gaining weight is advisable. Advice 1. Adopt natural ways of gaining weight 2. Start workout in gym at least for half an hour for 4 – 5 days in a week regularly. 3. Start with a balanced mix of cardio, weight training and flexibility exercises 4. Take natural high protein like egg, soya bean, pulses, meat, and milk. Choose food with nutritional calories like potato, banana and dry fruits 5. Drink 4 – 5 liters of water daily 6. Chew the food properly to make it easily digestible 7. Avoid excess intake tea and coffee after meal as they contain tannin which hinders absorption of minerals like iron Thanks