Praise be to Allaah.
Islam is perfect and comprehensive. Allaah says (interpretation of the meanings):
“… This day, I have perfected your religion for you, completed My Favour upon you, and have chosen for you Islam as your religion…” [al-Maa’idah 5:3]
“Say [O Muhammad]: ‘What thing is the most great to witness?’ Say: ‘Allaah (the Most Great!) is Witness between me and you; this Qur’aan has been revealed to me that I may therewith warn you and whomsoever it may reach…” [al-An’aam 6:19]
“And We have not sent you [O Muhammad] except as a giver of glad tidings and a warner to all mankind….” [Saba’ 34:28]
Allaah has told the believers that fasting is obligatory (interpretation of the meaning):
“O you who believe! Observing al-sawm (fasting) is prescribed for you as it was prescribed for those before you, that you may become the pious.” [al-Baqarah 2:183]
And Allaah has explained when the fasting should begin and end (interpretation of the meaning):
“… and eat and drink until the white thread (light of dawn appears to you distinct from the black thread (darkness of night), then complete your fast till the nightfall…” [al-Baqarah 2:187]
This ruling is not addressed to any particular country or type of people; it is a universal law, which also includes the people asked about in the question. Allaah is Merciful and Kind towards His slaves and has prescribed for them ways of ease to help them to do what He has made obligatory. For example, He allows travellers and the sick not to fast during Ramadaan, to save them from hardship, as He says (interpretation of the meaning):
“The month of Ramadaan in which was revealed the Qur’aan, a guidance for mankind and clear proofs for the guidance and the criterion (between right and wrong). So whoever of you sights (the crescent on the first night of) the month (of Ramadaan, i.e., is present at his home), he must observe fasting that month, and whoever is ill or on a journey, the same number [of days which one did not observe sawm (fasts( must be made up] from other days…” [al-Baqarah 2:185]
So every responsible adult Muslim who is present when Ramadaan comes is obliged to fast, no matter whether the day is short or long. If a person is unable to complete a day’s fast, and fears that he may die or become ill, he is permitted to eat just enough to keep his strength up and keep himself safe from harm, then he should stop eating and drinking for the rest of the day, and he has to make up the days he has missed later on, when he is able to fast. And Allaah knows best.