Glucose spike after mini fast

Hello everyone,

I do not have a diagnosis of diabetes and my A1C tends to the high normal - 5.4, 5.3, and 5.5. Nevertheless, I am extremely fascinated/interested/committed to learning about glucose’s and insulin’s role in disease genesis and progression.

I follow Peter Attia closely as well as others that many on here do as well (Rhonda Patrick, Jason Fung, Bret Scher, and so on). I believe we are finally learning (or as Taubes may argue, re-learning) so much that is truly useful. Still, we have a long way to go toward educating the public.

Two or three times a year, I will fast for 24-36 hours. Yesterday, I “fasted” for 22 hours, and I broke it by eating three portions of different types of salads from the salad bar at Whole Foods, a large handful of homemade chips, and 2 pieces of white toast. And a vegetable-rich smoothie. At about 50 minutes, I checked my sugar and it was 214. I have never seen my BG that high. At 1 hour 25 minutes after the last bite (30 min after the first BG check of 214), it was 99.

While I would like to do CGM, I think that that’s maybe taking things too far. My question is, is a BG of 214 followed by a 99 reading 30 minutes later an indication, in your opinion, of insulin resistance/hyperinsulinemia? Are there other “proxies” for understanding what one’s insulin outflow may be?

For what it’s worth, here’s what Peter Attia has to say about blood sugar after a fast:

"A group out of Japan in 2017 took 10 healthy adults, provided them with continuous glucose monitors (CGMs), and provided them with isoenergetic meals for 4 consecutive days. On days 1, 2, and 4, participants ate a higher carbohydrate diet (i.e., 3 meals/day of ~120 gm CHO/meal for males), while on day 3, they ate a CHO-restricted diet (i.e., 3 meals/day of ~10 gm CHO/meal for males).

"What they found was that one day of almost complete CHO-restriction led to post-meal glucose surges the next day when eating a higher carbohydrate diet. I must confess, I was surprised to see this result after such a modest period of CHO-restriction.

“As squishy as the term insulin resistance can be, what I think is going on here is some form of insulin resistance occurring in the muscle. Fasting or CHO-restricted diets lower insulin levels, which leads to more circulating FFAs that can be utilized by muscle, and triggers insulin resistance in those muscles, sparing more glucose for the brain and red blood cells in the bargain.”

I’m just interested in hearing peoples’ opinions, if any. Thanks!

I have never heard of any of these people you are name dropping but I eat, dose and exercise based on my CGM and digital scale.

In order to keep my blood glucose flat lined most of the time and keep my weight within 2 lbs at all times, I IF (intermittent fast) pretty much on a daily basis. If my weight in the morning is over my base target by even .1 lbs, breakfast is skipped. If morning weight is over target by more than 1.4 lbs, then skip all meals for the day which normally gives me a 36-41 hour fast. I often eat OMAD (One meal a day) at lunch time.

Fasting really helps keep my blood glucose flatlined and no, I do not spike at all after a 16, 36 or 41 hour fast. That may be because I am on a low carb diet of no more than 25 carbs per meal, eat about 800 calories in meal plus nuts and few other snacks to maintain weight.

Maybe I don’t get the results you are experiencing because “mini fast” is just part of my normal weekly routine and have honed my routine to achieve consistent results.

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I don’t trust that smoothy. I blame the smoothy.

I would make sure that you didn’t have sugar on your fingers when you checked BG.

I would run the test again eating food from home and not supplied by a restaurant (its surprising how much sugar is in things that you might not expect). Eat a banana and a sandwich…something normal and predictable.

You shouldn’t have a postpranial of 214.

I’ve read a fair amount about this phenomena and my personal experience is also consistent with this idea. Much has been written about the “second meal effect.” It basically says that the glucose effects of a meal are often felt also after the second meal.

I realize that you don’t take any external insulin so your body functions different metabolically than someone like me who does take exogenous insulin.

Here’s how I understand your circumstance. You fasted for 22 hours and your glucose metabolism was given a rest. Your pancreas secreted less insulin over this time than the previous day where you ate normally. I’m thinking your glucose levels during the fast were well-behaved.

Now, with your glucose metabolism and pancreas relatively relaxed due to no challenges from meals, it then does not responded well to the subsequent first meal after the fast.

Your choice of foods, by the way, was a large challenge to your glucose metabolism. While many salads are low carb, if you chose starchy veggies like corn or beans, then it would contribute to higher post-meal glucose. The chips, toast, and vegetable smoothy, however, were like throwing gasoline on a fire.

Since you seem to like doing personal experiments, perhaps you could try eating the same foods without the preceding fast. If the “second meal effect” was in play for your “fast then feast” experience then your post-meal glucose levels without the set-up fast will be lower by comparison.

The first question I would ask, as someone else noted above, is whether you thoroughly washed and dried your hands before the BG checks. If I were doing this n=1 experiment and saw an unexpected BG reading, I would repeat the test to minimize the possibility of a strip error.

By the way, I think using a CGM for a few weeks would be an excellent personal education for you. Even though you are not diagnosed with diabetes, you may very well have some glucose metabolism weaknesses. If I were you, I would be happy to pay out of pocket for this education.

I’ve learned a lot from the people you mention. I’ve also learned that just because someone lives with diabetes does not necessarily mean that they take the same level of interest as I do in the topic of nutrition and diabetes. As a group, we likely take greater interest than the background population in how food affects our glucose levels but people are busy with other aspects of their lives and don’t necessarily focus on this part of their health.

I think there is a big difference in glucose response in people without diabetes plus those with adult onset diabetes who still have some beta cell function and those with early onset who have NO beta cell activity at all. I have no proof of this, but feel there is a rebound effect in some ways comparable to that of reactive hypoglycemia.

Totally agree. After re-test with clean fingers, and eating food with known value, if postpranial is still over 150, I would want to go for a blood glucose test to have the lab run the check after a fast with a known carbohydrate load. Then I would also go to another facility to repeat test and for an A1C test as we know that many labs have not yet had their equipment and protocols certified for A1C tests and the results can typically be off by as much as 1%. This way at least you can be sure that the lab information is reasonably accurate before going on a wild goose chase of assumptions and possibilities.

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Thanks! I was just very very surprised at the high reading, and I think it is indeed because I broke the ‘fast’ with so many carbs. (I actually call what I do normally - eat in a 10-12 hour window - as time-restricted feeding, and me personally consider a fast to be at least 24 hours. I know Fung uses the word loosely, and Attia is much more a stickler about it.) I apologize to folks for references these people, Attia and Fung, but they have been my virtual teachers and I have learned so much from them - they are for me indispensable.

My fingers were definitely clean before the sticks. I have a glucometer bc I work in healthcare, and as I said at the top, I’m fascinated by all of what we are learning now about the role of glucose and most especially insulin. The amount of knowledge gained (or, again, as Taubes would say, re-learned) in the last 15 to 20 years is staggering, and worth everyone paying attention to.

Thanks so much everyone for the responses. I tend to agree with what Terry said and think the BG spiked because I had been fasting & for the reasons he elaborated. I absolutely must be much more careful in how I break a ‘fast.’ I tend to go for the prepared foods … because I’m hungry and they are, well, prepared! Higher fat and protein foods would take more time, but still, I need to do it because the way I did it yesterday I am potentially undoing whatever benefits I might have gotten from not eating for 22 hours. Specifically, I know we all respond differently to different foods, and chips are something that for me can definitely cause me to spike.

I am interested in doing the glucose tolerance test, for sure, something I’ll probably do on my own. And I would like to do a CGM, just not sure if I’m quite “there” yet.

Good point - and yes, I do this, too. It’s never been that high. The highest I’d previously seen my BG was 156.

I think I may be closer to this now than I was whenever it was I first wrote in. The reason is that my A1c yesterday was 5.7. (Estimated avg glucose was 117) I realize there’s a margin of error with these tests, but that number has been going up on me, not down, unfortunately. It’s the 2nd lab A1C I’ve done - the other two A1C tests were kits from CVS which I consider of decent enough quality. I’m not looking for 100% precision.

My fasting BG yesterday was 88, usually it’s around 90 at lab draws. I am particularly interested in my insulin levels, something that’s very hard to measure. Lots of reading lately on hyperinsulinemia being diagnostic of diabetes; I find it all interesting. My fasting insulin was 2.9, so good. I would like to do an insulin challenge but have not been able to wrap my head around how to get that done, exactly. Especially if my doc will not order it. (I don’t know if she will.)

Anyway, I am now thinking of getting a dexcom g6 - see long link below. It looks like for about $543, I’d get three monitors that last three months. As a non-diabetic/non-diagnosed diabetic, I am trying to find out if I would 1) be able to even order this; and 2) be able to monitor the results myself.


ETA: Adding that my LP-IR score was less than 25. This is an insulin resistance marker. I don’t really know how to talk intelligently about this test. But very generally, it seems that all I’m ok insulin-wise, but things are inching up in the BG dept. Not exactly sure how this can be, if it has real meaning, or what.

After doing some basic Internet searching yesterday, it seems CGMs are hard to come by for the worried well. And I’m finding that among diabetics there is no love lost for non-diagnosed diabetics using them!

So I have to make my own CGM, which I did this morning.