Can you chew no-calorie gum while fasting?

With a trembling voice I would say yes, if you are worried that your bad breath might annoy others.

I think chewing no-calorie gum can be comparable to using the miswak which was used by the Prophet (PBUH) while he was fasting, which makes analogical reasoning (Qiyas) applicable.

عن عامر بن ربيعة: "رأيت النبي صلى الله عليه وسلم ما لا أحصي يتسوك وهو صائم".

Narrated Amer bin Rabi'a, "I saw the Prophet cleaning his teeth with Siwak while he was fasting so many times as I can't count."

I think bad breath in Ramadan is something that should be controlled. It is true that there is a hadith that says "The breath of a fasting person is more pleasant to Allah (SWT) than the scent of musk." Well, it may smell like that to God, but not to us humans.

This hadith motivates a person who is fasting to be patient and it also motivates a person who smells his bad breath to be tolerant.

But the purpose of fasting is to train a person to persevere hunger and thirst. It doesn't mean that bad breath is necessary.

Brushing your teeth and chewing no-calorie gum can be the modern equivalent to miswak. Miswak has a taste and it is likely that using it will give you a few calories, yet it was allowed by the Prophet during fasting. Are we to stick only to what he used for caring for his teeth and breeth?

There is no reason why we can only use ancient remedies even though there are modern solutions. If the Prophet had lived these days, I think he would have allowed for no-calorie gum to remedy bad breath. When I wonder, "What would Muhammad do?" I would think he would be understanding. That is how I perceive him.

I recently went to get a facial while I was fasting and I was worried that my breath would annoy the esthetician. She was not Muslim which made me even more self-conscious because I didn't want her to get a bad impression about Muslims, Ramadan and fasting. The Prophet was always sensitive to offensive smells and was willing to make exceptions to the rules occasionally to ensure that no bad odors came from him. Besides using siwak while fasting, he asked people who had eaten foods that cause bad odor, such as onion and garlic, to avoid going to the masjid so as not to annoy others. He was once told by one of his wives that he had a bad smell because of something he had eaten. He promised never to eat it again. He later went back to eating it when it became clear that it was just a jealously issue of another wife whom he had eaten it with.

Therefore, I believe that there is enough evidence from the tradition of the Prophet to suggest that avoiding bad breath is a justifiable ground to allow small amounts of sugarless gum while fasting if you need to get in close proximity with others while fasting.

Chewing gum (especially sugarless gum) has been shown to be good for your teeth, good for stress reduction, good for improving memory, good for controlling hunger, and good for alertness if you are trying to stay awake (say while you are driving).

Nevertheless, I would use gum sparingly while fasting and only to control bad breath.

I wouldn't chew gum too much because it stimulates acid secretion in the stomach which prepares it to receive food, but when nothing comes, it makes you feel hungry.