Fasting as T1D with high insulin resistence


I am aT1D on an insulin pump using CGM and I have about 100 lbs to lose. T2D runs in my family and my endo says my insulin needs definately reflect insulin resistance.

I have tried intermittent fasting (IF) about three times per week over the last month and lost a good amount of fat. My fasting days would start after dinner but I would usually need to stop the fast before dinner again, say after 18-20 hours, because I start to get confused & start to make cognitive errors. My BG was not low.

I am hoping other T1Ds have had experience with IF and even multiple day fasting. I am try to figure out how to go past the 18 hours without having cognitive problems. Also I am wondering if other T1Ds found that their basal needs changed on multiple day fasts. Finally I am wondering if diabetic ketoacidosis DKA was even an issue on multiple day fasting.


Hello, I do a fastmimicking diet of 5 days once a month. I have been doing it for almost a year now. My usual basal needs are about 4 to 5 units a day, when I fast it goes down to less than a unit per day. I take about 3 units per day of bolus with the food (750Kcal/day). So yes a big drop in insulin needs and no dawn phenomena for me while I fast. I do not know if I produce more insulin as it was claimed in the original publication on fastmimicking dieting, or if it is due to the fact that while your body is on starvation mode, the liver does not distribute the sugar as it usually does. I really love what fasting has done for me, in terms of health (low fat, low cholesterol, etc) The only thing I trully detest is the fact that I sleep very very poorly while fasting. I have found that you get used to the fasting and I do not have the low energy and slow mind that I use to have when I started, now, I actually run (very low intensity runs, burning only fat) almost every day of the fast and it is fine. As far as ketoacidosis, I go as far as ketosis (not ketoacidocis, since my blood sugar is fine) I go as far as 3 unit (on the libre reader) and no problem at all…Hope this helps

Thanks Nicolas for the description of your experiences. In terms of the fasting mimicking diet (FMD), are you doing ProLon or a DIY?

(I’d like to do the FMD ProLon but it is simply too costly. And in terms of DIY FMD, I am not sure how to develop that.)

Unrelated to fasting, but if you’re having insulin resistance and want to lose weight, maybe consider metformin? T1s are increasingly using it in addition to insulin, and it helped me with both of those issues. I take 1000mg of metformin ER 2x a day, and my insulin resistance, particularly my basal dose and my dawn phenomenon, went down, and I relatively easily lost weight until I got back to my pre-insulin-resistance-starting to-creep-up weight (would still like to lose more, but I feel much better at this weight).


Simply because I didn’t always have enough time to prepare and eat meals while I was in graduate school, I would sometimes go up to four days in a row without eating. I checked my blood sugar often during these periods and would take only a background dose, and the blood sugar remained fairly stable. It was only by the fourth day that I would really start to feel uncomfortable, especially when I had to climb a hill en route to the university. I didn’t do it for weight loss, since my body mass index has stayed around 19 for my whole life, and I didn’t lose much weight either during these fasts.

In my (not so) humble opinion, you have to be crazy to pay over 200$ for 750Kcal a day, I do it my self, it is quite easy to find online what to eat, google how to do a FMD, you’ll find tones of spread sheets.

Hi cardamom,

I actually already use metformin at the dose you mentioned & it has helped in reducing my basal needs especially. It also helped me lose about 50 lbs about six years ago while doing Weight Watchers but I slowly gained that weight back. It still helps though so I agree that it helps.

Ah ok, well good luck with your fasting! I know some of the T1s around here have also experimented with other T2 meds with varying effects—might be worth checking out some of those threads too if you haven’t and are interested.