Hello, luupski – If we try to get a workable comparison between 7-day and 10-day cycles, I think we should think in terms of a three-week block of time. (The actual lowest common denominator of 7 & 10 is 70, but, to my mind, that’s not a feasible number of days to consider.)
Three weeks on a 5:2 schedule would give you 6 fast days spread over 21 days
(3x 5:2 = 15:6 = 21 days)
The nearest equivalent on a 4:6 rota is two blocks of ten days, i.e. 20 days, and, so, over those two blocks of ten days you need to fit in 6 fast days (to keep roughly on target, according to the 5:2 system).
It would be up to you to decide which of your various different days would be most suitable for a fasting schedule and whether you wanted the fasting day to be for just 24 hours or the 36-hour block that many regular 9-to-5 workers fit in by doing the ‘sleep-fast-sleep’ pattern (where, if Monday is a fast day, the 36-hour countdown starts whenever the eating ends on the night before, Sunday, and continues during the sleep Sunday night / on Monday: max. 500/600 cals is eaten during the day, with full fasting starting again after Monday’s last food and continues during the sleep of Monday night / normal non-fast day, Tuesday, starts with first food intake that day : total time, roughly, 36 hours).
Also, you would have to choose whether fasting on working days or rest days would be best for you. Most people find it easier to fast when they are busy, too occupied to dwell on food. Presumably your sleeping patterns vary all the time. I’m afraid I can’t get my head around those complexities but you know your own habits and patterns so, hopefully, you can sort out a schedule for yourself. It takes most people quite a time to find workable 5:2 timetable for themselves, involving some period of experimentation, just using trial-and-error. I imagine that will be even more true for you but I wish you every success in your efforts.

Hi, luupski – Yes, I can see how finding the right choice of days is crucial for you within such a varied work pattern. If you feel 4:1 is workable, I would say try it and see what happens. If your reason for adopting the Intermittent Fasting system is in order to gain the health benefits then 4:1 should still give you that. However, if you are looking to achieve weight-loss, 4:1 may well be slightly slower or less effective (compared to the 5:2 pattern recommended for people working a regular-hours pattern) because 4:1 means that over 20 days you would fit in only 4 fast days instead of the 6 fast days that occur on the 5:2 pattern over a similar period (21 days). Ideally, to match the 5:2 plan, you would need to fit 3 fast days into your ten-day block rather than just 2. Do what feels acceptable and manageable to you. I think the system calls for a bit of creative thinking and adaptation in the light of your shift patterns. Any initial plan can always be changed in due course, if you feel the need. All best wishes.