He is afraid that he may become sick because of being underweight; is he allowed not to fast during Ramadan?

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Check below answers in case you are looking for other related questions:
Is it permissible for him to break his fast because his work is difficult?
Can he break the fast because his work is too hard?

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Related Answers:
Her family forced her to break her fast because she was sick – were they sinning? Can she fast if she wants to?
He was not allowed to eat because of sickness; does he have to fast?
Amount of fidyah to be paid by one who is unable to fast because of old age or sickness
Is it permissible for him to break his fast because his work is difficult?
Can he break the fast because his work is too hard?

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