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I can understand your concern. You are thinking in the right way. Indigestion may affect weight gain. Your lifestyle, food habits and lack of physical activity may cause indigestion, and it leads to acidity. Take the following ayurvedic medicines and follow these instructions. Take Chitrakadi Vati (Chitraka with Vida Lavana) two tablets and chew it before food.
Take Avipattikar Churna (Trikatu with Haritaki) three grams with Kamadugha Rasa (Amrutha satwa with Svarna Gairika) one tablet twice a day after meals. Take Drakshasava 15 ml (Draksha with Lavanga) twice a day with an equal amount of water half an hour after meals. Take these medicines regularly for one month.
Avoid eating spicy and fried junk foods. Avoid smoking and drinking if you have these habits. Do regular kapalbhati, Mandukasana, and pranayamas like anuloma vilom and Nadi shodan. Do these things and provide your valuable feedback after fifteen days.