Brief Answer: exercise Detailed Answer: Hi and thanks for the query. I am Dr. Alok and very pleased to be assisting you with your health questions today. Best way to increase muscle mass is exercise with proper diet, its not by quantity of food, it is related to quality of food. Donot fall on various advertisement who claims that they will increase weight in one or two months-- they are fake and witha lot of side effect. You should join a gym and a good trainer and take advice. mean while I advice you to go for some investigation-- Thyroid function test, RBS, CBC, LFT. to rule out ant medical disease. Hope this helps and provides answers to your question. I wish you good health. Dr. Alok

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