Keto Cheat Meal: How Long is Blood Sugar Elevated?

Just wondering how long your BS will stay high after you eat something you shouldn’t have. (Read: like ice cream or something) will it be messed up for a couple of days?

Also, I’ve read that keto is really bad for T2 diabetics, but then other people follow it. What say you lot?

I think this is highly individualized, and also depends on what you eat. Eating oatmeal compared to eating ice cream will have a drastically different effect.

Just from my experience, I coached a T2 diabetic for 2 years. We we able to get him from 400lbs down to 240lbs with carbs, and only had to do keto to get him below 200lbs. We did keto for about 4 months and it got him down to 195lbs, then we slowly started adding carbs back in. Over the course of our time together he was able to cut all of his medicine and was no longer T2.

Are you on keto now? If so, why?

Elevated Blood Sugar

For most individuals, eating something you shouldn/t on the Ketogenic Diet is going increase you glucose blood sugar for a couple of hours afterward. It will then should drop back down to normal levels.


The information you read on Keto being bad for Type II diabetics is incorrect.

Carbohydrates are the issue for Type II Diabetics, not protein nor fat. Limiting carbohydrate intake, especially high glycemic/insulin index foods can often put a Type II Diabetic in remission.

The Irony of The ADA, American Diabetes Association

What make no sense is the ADA recommendation of a Type II Diabetic’s diet being carbohydrates.

It amount to recommending someone who’s Lactose Intolerant drink milk or someone with Celiac Disease consume gluten.

A low-carbohydrate, ketogenic diet to treat type 2 diabetes

“The LCKD improved glycemic control in patients with type 2 diabetes such that diabetes medications were discontinued or reduced in most participants. Because the LCKD can be very effective at lowering blood glucose, …”

This is one of many research papers on the benefits of the Ketogenic Diet for Type II Diabetics.

Type I Diabetes

The Ketogenic Diet is also being used, under supervision, for Type I Diabetics that need insulin.

One of the finding is that when Type I Diabetics are placed on a Ketogenic Diet, it reduces the amount of insulin they need to take.


He provides some good practical experience on this.

Kenny Croxdale

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If type II diabetics lose weight WITH carbs in the diet then they are going to reduce their insulin needs and insulin resistance. If they gain weight on a zero carb diet they very well may increase their insulin resistance. Replacing carbs with fat reduces insulin needs because carbs go down, but it increases insulin needs because muscle begin to store fatty acids, and stop making enzymes to burn glucose on a high fat diet. In fact, type I diabetics have been reported having nearly EQUAL insulin needs on a 80% carb diet as on a 25% carb diet with calories being equal, but their blood sugar fluctuations are virtually normal on 25% carbs while they tend to experience harmful fluctuations on high carbs. Type II diabetics report lower insulin and medication needs on a ketogenic diet, but this is because their body is still producing a significant portion of their total required insulin and a ketogenic diet avoids a rapid fast release of insulin that carbs require. In fact consider that a ketogenic diet that typically contains <10% of the carbs of an average non-ketogenic diet still requires half the insulin by type II diabetics who are still making much of their own insulin and it is clear that dietary fat raises insulin needs-just not “fast” over short periods of time.

Very low GI carbs like pasta cooked al dente, or pizza made with high gluten wheat can actually raise blood sugar for 8-12 hours in insulin resistant individuals. Even in non-insulin resistant individuals, low GI starches can require elevated insulin for 8-12 hours in some cases.

Also, even a pure fat meal raises basal insulin requirements.

Regarding Ice Cream and Oatmeal, I would actually expect a bigger spike with oatmeal since the fat in Ice Cream slows down the absorption of sugar. Dairy also in general has been shown to lower the speed of a blood sugar spike, as well as acidity and fiber. It probably depends on how unrefined the oatmeal is though. Sucrose actually requires less insulin than starch on a gram per gram basis because the fructose component can enter the liver without insulin, but it tends to make the liver release glucose over a 2-4 hour period.

Fat doesn’t spike insulin by itself, but it decreases the effectiveness of insulin because fatty acids are competing with glucose to get into muscle cells. There is only so much space for fatty acids and glycogen in muscle cells.

Technically, ketosis raises insulin RESISTANCE that is to say your body won’t handle glucose as well. Ketones also make the liver resistant to insulin since the liver is processing fat and making ketones. If you come off of a ketogenic diet and take in say 50 grams of carbs, your body will have to release enough insulin to turn off ketosis, and then the glucose still has to compete with fatty acids, and insulin also turns ON glucose burning enzymes in the body. You actually are not supposed to take a glucose tolerance test coming off of a ketogenic diet because it can produce a false positive result for type II diabetes.

Carbing out of ketosis should NOT be done with a 1-2 days of fast carb loading. Carbs need to be raised slowly over at least 3 days to avoid hyperglycemia (over 180).

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Type II diabetes has several mechanisms: insulin insufficiency, delayed insulin release, insulin receptor desensitization, insulin receptor malfunction, insulin resistance due to fatty acid storage and reduced ability to burn glucose, insulin resistance due to general obesity, high levels of counter-regulatory hormones like cortisol, growth hormone, adrenaline or even testosterone. In general I would not say that Keto is bad for type II diabetes, but just keeping carbs under about 150 grams a day and moving toward, or attaining a healthy body fat level can produce blood sugar values as good as those on a ketogenic diet. A ketogenic diet turns off glucose burning enzyme production in muscles and other cells and it takes about 3-14 days for that to normalize when carbs are reintroduced. The more carbs you eat, the faster you will adjust, but the more your blood sugar will be higher. Still, if you stick to low GI carbs, you can stay below any harmful level. It also helps to exercise MODERATELY before and after eating carbs. Intense exercise can actually raise blood sugar by stimulating cortisol and adrenaline. Ketogenic dieters often have their blood sugar RISE slightly during activity because of cortisol, and enough cortisol can turn up insulin enough to shut off ketosis.

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In simple terms: low carb is good for insulin sensitivity issues; no carb is better; and no calories (fasting) is better still. If you have read guys like Jason Fung, you will hear of cases where type 2 has been reversed in a couple of weeks of regular fasting.