But there are exceptions and exemptions for the people. those who are ill or in some journey or are old enough that they cannot bear fast or have any other proper and valid reason, they can break their fast or leave it.
Women, cannot fast during their shari’ leave and they have to fast for the counted days after Ramadan. They are not exempted fully from fasting. A woman who is carrying a child in her womb and who cannot fast due to this reason can fast after she gets well. Similarly people who are ill they are exempted from fasting and they have to fast after ramadan for the counted days.
ALLAH swt says in Quran;
Al-Quran 2:183-184
“O you who believe! Observing As-Saum (the fasting) is prescribed for you as it was prescribed for those before you, that you may become Al-Muttaqun.
Observing Saum (fasts)] for a fixed number of days, but if any of you is ill or on a journey, the same number (should be made up) from other days. And as for those who can fast with difficulty, (e.g. an old man, etc.), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day). But whoever does good of his own accord, it is better for him. And that you fast, it is better for you if only you know.”
Thus, there are two provisions, one for those are a in journey or ill they can observe fasts on some other days as a must. But for those who are ill and they cannot observe fast even after Ramadan because they are either too old or they are ill for some chronic disease, they can feed a poor on their behalf to equalize the fasting.
Fiqh Us-Sunnah
Ibn 'Abbas said: "An elderly man is permitted to break his fast, but he must feed a poor person daily. If he does this, he does not have to make up the days that he did not fast. This is related by ad-Daraqutni and by al-Hakim, who said it is sahih. Al-Bukhari recorded that 'Ata heard Ibn 'Abbas recite the 'ayah: "And for those who can fast [but do not], there is a "ransom': the feeding of a person in need" [al-Baqarah 185]. Then Ibn 'Abbas continued: "It has not been abrogated. [Its ruling applies] to elderly men and women who are not able to fast. Instead, they must feed one poor person on a daily basis."
But this rule should not be misused as we see people feeding poor and when they get well they do not fast saying that they are permitted. To alter deen in desire is a grave sin, this sin was done by previous nations and they are today, the humiliated ones.
Ibn Qudaamah said in al-Mughni (4/396):
If fasting is too difficult for an old man or an old woman, and will cause them intense hardship, then they are allowed not to fast, and they should feed one poor person for each day. If they are also unable to feed a poor person, then they do not have to do anything, for “Allaah burdens not a person beyond his scope” [al-Baqarah 2:286]. If a sick person has no hope of recovery, he is allowed not to fast, and he should feed one poor person for each day, because he comes under the same ruling as an old man. End quote.
Thus if a poor man cannot even feed a person for his fasts, then he is even exempted from that because ALLAH swt does not make din difficult for us to follow because HE is oft merciful. Those who are exempted from fast should observe the fasts after their situation is eased down and they should not make their own wishes dominated by islam.