Your weight should be according to your height. Calculate your Body mass index (BMI). BMI below 18.5 is underweight. BMI is calculated by formula BMI = Weight in Kilograms / (height in meters x height in meters). Maintain a BMI between 19 and 25. If it is in normal range then there is no need to gain weight. If you want to gain weight then gradual weight gain 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. You have lost more than 10% of your body. This is significant and needs to be investigated. Advice 1. Stop all kinds of gym supplement 2. Start workout in gym at least for half an hour for 4 – 5 days in a week regularly. start with a balanced mix of cardio, weight training and flexibility exercises 3. Take natural high protein like egg, soya bean, pulses, meat, and milk. Choose food with nutritional calories like potato, banana and dry fruits 4. Drink 4 – 5 liters of water daily 5. Chew the food properly to make it easily digestible 6. Avoid excess intake tea and coffee after meal as they contain tannin which hinders absorption of minerals like iron 7. Investigations a. Chest X – ray PA view b. Hb% c. ESR d. CBC e. TSH f. Serum sodium & potassium Consult a general physician for general physical examination of your body and further management. Thanks