Wednesday, September 16, 2009

Diabetics on a Low-carbohydrate Diet

Diabetes is a disorder of glucose intolerance. What happens when a diabetic eats a low-carbohydrate diet? Here's a graph of blood glucose over a 24 hour period, in type II diabetics on their usual diet (blue and grey triangles), and after 5 weeks on a 55% carbohydrate (yellow circles) or 20% carbohydrate (blue circles) diet:

The study in question describes these volunteers as having "mild, untreated diabetes." If 270 mg/dL of blood glucose is mild diabetes, I'd hate to see severe diabetes! In any case, the low-carbohydrate, high-fat diet brought blood glucose down to an acceptable level without requiring medication.

It's interesting to note in the graph above that fasting blood glucose (18-24 hours) also fell dramatically. This could reflect improved insulin sensitivity in the liver. The liver pumps glucose into the bloodstream when it's necessary, and insulin suppresses this. When the liver is insulin resistant, it doesn't respond to the normal signal that there's already sufficient glucose, so it releases more and increases fasting blood glucose. When other tissues are insulin resistant, they don't take up the extra glucose, also contributing to the problem.

Glycated hemoglobin (HbA1c), a measure of average blood glucose concentration over the preceding few weeks, also reflected a profound improvement in blood glucose levels in the low-carbohydrate group:

At 5 weeks, the low-carbohydrate group was still improving and headed toward normal HbA1c, while the high-carbohydrate group remained at a dangerously high level. Total cholesterol, LDL and HDL remained unchanged in both groups, while triglycerides fell dramatically in the low-carbohydrate group.

When glucose is poison, it's better to eat fat.

Graph #1 was reproduced from Volek et al. (2005), which re-plotted data from Gannon et al. (2004). Graph #2 was drawn directly from Gannon et al.


epistemocrat said...

"When glucose is poison, it's better to eat fat."

A good story to live by.

GoEd said...

For some more spectacular blod sugar curve improvements on low carb diet check out Helen Hesselmarks story at:

Quite interessting what she notes at the end of her story that even though there is an improvement in the HbAc1 (which is what most doctors look at) you are not able to see the difference in blod sugar spikes by just using HbAc1.

Robert Andrew Brown said...

Many thanks Stephan.

Another excellent find that is highly thought provoking.

Jenny said...

Nice find!

The diet used in this study is one that would represent an intake of 125 g of carbohydrate for the typical male eating 2500 calories a day.

The numbers in this study are still going high enough even in the lower carb group to produce complications over time--especially that fasting blood sugar.

Adding metformin would help a lot because it is far more effective for people low carbing than for the general population of people with diabetes.

Dropping carbs a bit lower would make a significant difference too.
I do not advocate extremely low carb diets not because they don't work--they do--but because over time most people find it extremely difficult to stick with them and diabetes is all about the long term, so a more moderate approach that is sustainable beats a perfect approach that isn't.

Most people can live very happily on 80-100g a day of carbohydrate without feeling too deprived, especially if they put some time into studying techniques for replacing carbs with reasonable alternatives. I have put together some suggestions and links here:
What Can You Eat When You Are Cutting The Carbs?

GK said...

Notice they had to leave the standard disclaimer at the end of their conclusion: "the long term effects of this diet are unknown".

Vin - NaturalBias said...

Despite this obvious information, it's a shame how many people rely on insulin and medication and continue following the same flawed eating habits that brought them diabetes in the first place. Thanks for sharing this compelling research, Stephan! And congratulations on earning your PhD!

gibby1979 said...

Have you looked at the latest issue of cell metabolism? It has an interesting article about the role of bile acids in the regulation of blood sugar and insulin. An interesting read, the comment on it has a terrible title "bile acids have the gall to act as hormones". I this is pretty relevant to the high fat diet as a method to fight diabetes

Steve Cooksey said...

Congrats Stephan on PhD!!!! Awesome work you do. I am spreading the word.

I'm type 2 diabetic who once was on 4 insulin shots a -0- insulin, -0- meds.

I went low carb and exercise...that's it!!!

Thx again,


Aaron said...

I would love to see the graphs of non-diabetic peoples, 10,20% low carbers vs kitavans. I don't think you can just assume it will be automatically better for the low carbers.

Stephan Guyenet said...


I've noticed that there isn't always a great correspondence between HbA1c and actual blood glucose. My HbA1c was 5.8% in 2008. That supposedly corresponds to an average blood glucose of 107 mg/dL.

I gave myself a makeshift oral glucose tolerance test. My BG didn't go above 106 mg/dL. I tested my post-meal BG religiously for a while, and it rarely broke 125 mg/dL. My fasting BG is 80-90 mg/dL, totally normal. My actual average BG over the course of the day is definitely lower than 107 mg/dL.


Agreed. In the glycemic index trials I reviewed a while back, there were several where average BG and insulin was different between groups but the HbA1c was the same or only slightly different.

Steve Parker, M.D. said...

It's curious that the HDL cholesterol didn't rise significantly in the 20% carb group. Most studies show an increase.

Aaron said...

HbA1c is starting to become an interesting statistic-- I've noticed other low carbers around the net who seem to eat a well-constructed low carb diet- and still seem to have high HbA1c levels.

There was some discussion that maybe there is less turnover of hemoglobin on a low carb diet, hense the higher HbA1c.

It's also possible that a higher avg HbA1c resulting from a lower carb diet is a shortfall of that type of diet.

I have a feeling that Kitavans have a low HbA1c-- stats anyone?

Ryan Koch said...

Stephan and others,

I just posted a commentary on this study on my blog and would be interested in hearing your thoughts.

The short of it is: low-carb works for diabetics. Great! What about low-trans fats; low sugar; low-wheat?

Maybe it's not the glucose that is the poison ...

Stan (Heretic) said...

Re: "It's curious that the HDL cholesterol didn't rise significantly in the 20% carb group. Most studies show an increase."

True! But only if they eat sufficient amounts of fat!

Low HDL is probably a telltale sign of a "botched" fatophobic LC diet: too much protein and not enough animal fat.

Bryce said...

Aaron said: I don't think you can just assume it will be automatically better for the low carbers.

You are absolutely right in that fasting glucose levels are probably just fine for the Kitavans and other pre-agrarian high carb eating peoples. They have no problems metabolizing glucose, because, even though they eat plenty of starch, they get if from low glycemic index foods (like sweet potatoes). More importantly, the intake of refined sucrose/fructose is almost nonexistent, and as Stephen has demonstrated thoroughly, fructose (in the doses Americans consume it) is what really causes insulin resistance over time - first by causing non-alcoholic fatty liver and corresponding hepatic insulin resistance, and then by the subsequent general insulin resistance that Stephan mentioned.

If all you ever ate your whole life was meat and potatoes, you'd likely do quite well. But once you've poisoned yourself for years with 60-80lbs fructose/year, your body simply can't handle large quantities of even low-glycemic index foods.

I think the less-informed low carb view point is that carbs are inherently evil (I certainly used to think so). But as Ryan points out, glucose isn't inherently poisonous. However, it has the damaging effects of poison on people with insulin resistance and hyperinsulinemia - i.e. metabolic syndrome. For these people, glucose is highly damaging, precipitating increased insulin resistance and beta cell damage. Also damaging are wheat (for the autoimmune problems, including possible links to autoimmune causes for type I diabetes), sugar(fructose for it's effect on the liver), and of course trans fats.


Bryce said...


Many low-carbers have somewhat elevated fasting glucose because their livers are actively engaged in gluconeogenesis. Once they delve into Ketosis, their bodies become adept at producing glucose from protein for the brain and for the replenishment of glycogen stores. This can, at times, be observed in Marathon runners, post race, who have elevated blood glucose long after their glycogen stores are thoroughly depleted.

I wonder if this wouldn't account for the elevated HbA1C levels Ryan mentioned?


Stephan Guyenet said...

Hi Steve and Stan,

The high-fat diet was based on monounsaturated fat. That probably explains the lack of increase in HDL.

Ryan Koch said...


You said, "...glucose isn't inherently poisonous. However, it has the damaging effects of poison on people with insulin resistance and hyperinsulinemia - i.e. metabolic syndrome. For these people, glucose is highly damaging, precipitating increased insulin resistance and beta cell damage."

While I agree that glucose is damaging to folks with metabolic syndrome, I'm not so sure that all glucose is damaging. Carbohydrates from wheat and sugar may not have the same effect as potatoes and rice, for example. Wheat and sugar -- as you know -- have inherent qualities that make them less benign foods.

So, really, the question I have surrounding successful low-carb research is this:

If the participants in the studies were to eat the same number of carbs yet restricted or eliminated detrimental carbs -- wheat and sugar -- as well as other harmful foods like trans fats, would the same results (i.e. balancing blood sugar, improving blood lipids, etc.) be achieved as are seen in low-carb trials?

Bryce said...

Obviously glucose which is accompanied by gluten, fructose, and other things our metabolism isn't suited to deal with is worse than glucose alone, but it doesn't mean that the pure glucose isn't harmful.

A severe diabetic IS, in my opinion, doing some damage to themselves when the eat a potato, because their body will endure a damaging insulin spike. It won't be as bad as that induced by a piece of corn bread, but it won't be as benign, in my opinion as a spike induced by a fat source.

I think after time, a diabetic might restore enough insulin sensitivity to enable them to process brown rice and sweat potatoes effectively.

Diana said...

Hello Stephan,
As a Type 2 diabetic, I just wanted to weigh in with my experience.
I was diagnosed in Jan 2009, with an A1c of 7.2. But, I began a low carb way of eating about 6 months PRIOR in July 2008, after reading your blog, Blood Sugar 101, and others, it just seemed the right thing to do. I knew then, even without a Dx that most likely I was diabetic.(I am sure that had I not been eating this way, my A1c at diagnosis would have been much highter). I will admit that it was easier to "cheat" before my Dx, and I did it more often. Somehow, being diagnosed, checking blood sugar 4-5 (sometimes more)times a day keeps you on the right path!
Anyway, since Dx, I have been eating about 30 grams of carbs a day in the form of leafy greens, and other low carb veggies. I also take 2000 mg of Metformin ER, which helps control my fasting BG.(To a degree, but with my N=1 study I have going here, I can say that I think being low carb defenitely keeps my fasting on the higher side of normal due to gluconeogenesis, I think Bryce was touching on this in an earlier comment). I eat my fill of saturated fat in the form of grass-fed butter (Kerrygold), virgin coconut oil and ghee. I eat moderate protein, and I practice intermittent fasting usually 2 days a week. I also eat "clean", all whole foods that I prepare myself. No processed foods etc.
Well, to get to my point, my A1c was 7.2 at Dx in Jan, 6.4 in April (1 month after rotator cuff surgery), and in August was 5.1!
I am lucky to have found a doctor who supports my eating, mostly because she can't deny the facts. A 5.1 A1c in a diabetic is a really good thing! I know I am not "cured", because if I eat something starchy my glucose will rise, but I guess I am really well controled you could say. It is a shame that the ADA tells diabetics to eat so many carbs. People deserve the chance to help themselves as I have. I give much thanks to you, Stephan, as well as Jenny from Blood Sugar 101, and anyone else that has put this information out there. You guys are saving lives!

Stephan Guyenet said...

Hi Diana,

Great story, glad to hear you've been able to control your diabetes so well!

trinkwasser said...

"Notice they had to leave the standard disclaimer at the end of their conclusion: "the long term effects of this diet are unknown"."

Yeah it's not as if we weren't doing this for a few millennia before dieticians were invented eh?

Hey, under 200 mg/dl is "not diabetic at all" so by those standards these folks are mere beginners.

You're spot on about the liver

not a lot of people know that. My trick liver used to over or underproduce glucose at different times of day, it only has to be out by a mere 5g for your BG to double. Running on (saturated) fat and ketones as fuel seems to have greatly reduced the liver's attempts to intervene.

More from the estimable Jeff Volek, demonstrating cardiovascular improvements in both the usually measured and some not usually measured factors

lizabaker said...

Haha. The long term effects statement is laughable! Surely a to go for low carb diet plan.