"The Warrior" diet, they call it. There's lots of restrictions and nuances, variations, and versions. But I only follow it very loosely. I eat after 12PM, have dinner around 5-6PM and steer clear of carbs where possible (i.e. junk food, bread, pasta, potatoes etc.) So it's really fasting combined with low(er) carb, I suppose.
I drink coffee (with a dash of unsweetened coconut milk and sometime a little pure cocoa powder #flavonoids), water, and tea - because I'm not a sadist... and mornings are hard (strictly speaking, you can only have zero-calorie liquids when fasting i.e. water and plain tea - maybe black coffee at a stretch). But like I said, I keep it simple. Also I get on the diet soft drinks (soda? for all the 'merican reading.) as well. They're zero calorie, and carb, and they help curb my monster sweet tooth. Lesser evils...
Now, logic - and a lot of research - tells us that fasting for an extended period has A LOT of effects on the body. Some people do it for weight-loss, 'detox', clarity of mind, better biochemistry, autophagy - the list goes on. I'm not bothered with any of that (though if it happens anyway, all the better). The main reasons I do it is to increase my insulin sensitivity, reduce my total daily dose of insulin (which is easier with higher sensitivity anyway) and the spikes - so overall better blood glucose control - and to help lose weight.
And it works. Insulin sensitivity increases. Your basal goes down. Your boluses are smaller for the same amount of carbs. And you lose wight (if you're doing everything I do and try not to snack - even healthy ones can blow out your calorie intake if you have too much) It's good. But, there are other - unpredictable - side-effects.
Enter protein bolusing.
I was always told you don't need to bolus for protein and fat. Type 1 diabetes 101. Broad strokes of course - get into the fine detail enough and you can bolus for any food. But the effects on blood-glucose are negligible enough, that you don't need to bolus for a steak or wedge of cheese, unless, it turns out - to my utter bewilderment, given all the information I had to this point - you fast and eat low-carb. Then your (at least MY) body treats protein like it's a big 'ol helping of pure, white, table sugar. And so, you have to bolus. For protein. It's trash. Now, maybe this isn't news to you, but to me it was a world gone topsy-turvey and I was figuring out by diabetic body fall over again - like a brand newbie T1D, fresh off the rubber-stamped production line.
Now, if that were it - wouldn't be SUCH a big deal, I hear you, just another routine, (and what's T1D if not a bunch of little routines?) that would be adaptable. BUT, because T1D likes to take the piss, and keep us on our toes, it's not as easy as just bolusing for protein. 1:1 cabs:protein only works on the first meal, it would seem, for me ie. when i eat for the fist time each day around midday. After that - things go sideways for me. I found this out the hard way - as we all do with new things - and it ended in the mother of all lows.
I stated with one of those 100g 'lo-carb' bars. 4g carbs and 40g protein (and a whole bunch of other fake fibre and sugar replacements, chemicals, and... poisons, probably.) So I dosed for 45g of carbs (round-up and I'm on 10:1 ratio for carbs), so it was 4.5 units. And magic - after about 3.5 hours when it's pretty much decayed, I was at ~4.5mmol (times by ~18 for your mg/dl number). Perfect. Now that bar isn't a real meal (it's about 380 calories). I needed proper food - the bar was just a test. Now that my bolus was done, I was safe to eat again without any Beautiful Mind-level maths. So (don't judge me) I cooked up 500g of stir-fry lean beef (that's about 105g protein) on a bed of bean-shoots and baby spinach (say another 5g protein/carbs total.) With my ratio, thats 110g = 11 units. No oils and little to no fat/s. So I bolused and ate. All looked OK. I was still trending upwards for about 40 minutes (albeit slowly, comparatively speaking to my low-carb bar.) But then... PANIC STATIONS! IT DOESN'T WORK THE SAME, THE SECOND TIME! I'M GONNA DIIIIIIE!
Needless to say, it took a downward turn. In the next 40 minutes, I plateaued and then dropped 3 points. I was still in my testing mindset, so I don't want to over-do it and have no idea where I am at re: bolusing for protein in the future. So I measure out 10g carbs (white table sugar is quickest and simplest pure-carb source I had on-hand,) eat, and wait. 15 minutes go by - I'm still dropping (2.8mmol now) but it's slowing. Eat another 10g sugar. Wait. Looks like that's arrested development (*smirk*). 20 minutes later, I'm up 2 points and borderline back in-range (4.5mmol). But, I figure I'm not out of the woods yet - only 2 hours since I bolused, so still another 90 minutes to 2 hours before the insulin has fully decayed. For those of you keeping track (105+5+10+10)/11=11.8g:1U. And that's pretty much where it stayed. I levelled out and was able to get to bed (at like 1:30AM on a Sunday night...)
So, that was my learning curve. Everything else is pretty much the same. Fasting and low-carb diets make you (or me, at least) protein-sensitive. Shouldn't really be a surprise. The initial protein intake, my body treats as carbs... I assume because it has none, so my liver just pumps it out asap! and it prefers that, to fat or keytones. So it coverts it to glucose right-quick and I bolus 1:1 protein-for-carbs. After that, it's like I haven't been fasting anymore. My blood's all sugary again and my liver's all stocked-up. So subsequent protein is not treated like the belle of the ball anymore. It's still favoured, but it's the poor cousin. And so I still bolus for it, but the ratio goes up a bit. For me, it goes from 10:1 up to to 15:1-ish.
For those of you that made it this far, here's a little visual - a pretty picture of the the night I learned I had to bolus for protein.