I cannot speak for other religions but Judaism certainly presents some challenges for a person with Diabetes. I grew up traditional orthodox and became more observant in my teens. What that meant throughout my formative years was strict observance to the dietary laws (kashrut), building a temporary dwelling on Succot, fasting on Yom Kippur, cleaning the house for Passover (and changing over the the "passover set" of crockery, pots and pans, and cutlery, and eating so much eating.
Yom Kippur is the most holy day of the year. It is the day of atonement, we fast for 25 hours, pray in synagogue all day and at the end of it we are forgiven for everything we have done wrong over the year. We wish each other that they should be inscribed in the book of life. Many people who observe nothing all year observe Yom Kippur. The synagogues are overflowing, some reaching out specifically to the "Once a year Jews". Here in Israel there is an additional part of the festival that you do
not get anywhere else. Everyone (ok not everyone - doctors and critical
workers may have to work) is off work. People will still fast but often not go to synagogue, they will walk the streets. And I mean the streets, people will be out on their bikes too. There is an unwritten rule that people do not drive for the whole 25 hours of Yom Kippur. The streets are alive with people wandering with nothing else to do. It is quite an experience. Though I would suggest to any potential tourists that they do not come at this particular time as there is literally nothing to do (except of course walk the streets).
Yom Kippur is not the only fast day on the calendar there are 6 more. Only 1 of these other than Yom Kippur, is for 25 hours (and is the summer, which is hard work) the rest are dawn till dusk. Before Yom Kippur and after there are big meals, as you might expect. This presents a double problem of balancing taking insulin for the meal, as I talked about in part 1, and getting it right for the fast. The first year I after I was diagnosed I checked with my medical team and my Rabbi whether I could fast. I did. I checked my BG every hour and I had dextrose tablets on me in case. I was fine. Probably because I was still in my honeymoon period. The trick was not to take much insulin at all.
The following year I had moved to Israel, and my Rabbi called me up a few days before the fast. He said that some Rabbi that he knew of and respected had taken out a full page advert in a religious newspaper. The advert said that under no circumstances should a Diabetic fast on Yom Kippur. Well that solves that one. I think something may have happened to someone who tried to fast the previous year. As a result, under the law of Pikuach Nefesh (saving life) Diabetics are now prohibited from fasting on Yom Kippur. He went on to say that not only should I eat, but I should eat proper meals as if it was a regular Jewish festival (ie not just enough to keep my alive).
This makes Yom Kippur weird for me, I am in synagogue praying but not starving, I am thinking when am I going to skip out and get some lunch. I put much more effort into my prayers as I cannot fulfil the commandment to fast, despite being told that because I have to eat, then eating is counted as if I had fasted. It's a strange religion sometimes, but it can be bent so that I am able to manage my disease and still observe what I wish to observe.
Live long and stay healthy.