Fibre on a ketogenic diet
- High fibre foods are often high in carbohydrates which can be problematic for people with diabetes or those trying to achieve ketosis.
- People aiming for a low carbohydrate diet often avoid all carbohydrates, including fibre, however this may not be optimal for gut health or overall nutrition in the long term.
- This article highlights nutrient dense, low carbohydrate sources of fibre that will have a minimal effect on blood glucose levels while helping to support gut health.
Dr Michael Ruscio
The human gut and the bacteria that inhabit it are still largely a mystery. However the latest research indicates that it is important.
I recently heard an intriguing information-packed interview with Michael Ruscio on Episode 985 of Jimmy Moore’s Livin’ La Vida Low Carb Show where he said that:
- Some people don’t do well with a very low carb approach in the long term;
- Some studies indicate that a very high fat diet can lead to increased intestinal permeability (aka leaky gut) which can lead to insulin resistance;
- In spite of the possible risk to optimal gut health, Dr Ruscio advises his patients to use a LCHF approach to manage blood glucose and weight, particularly for those who are insulin resistant;
- His preferred approach is to start patients on a low carbohydrate autoimmune protocol and slowly increase carbohydrates to find their tolerance level for carbohydrates where they stop benefiting in terms of body weight or body fat; and
- People on a low carb diet may benefit from a diet high in fibre / prebiotics / FODMAPs to promote microbial diversity and improve insulin sensitivity.
While some people believe that it is beneficial to try to manipulate the firmicutes : bacteroides ratio  or some other feature of gut microbiome, Dr Ruscio says that this is far from settled science. What we do know is that a more diverse population of gut bacteria will reduce the probability that one strain of bacteria will take over our gut and become dominant (i.e. overgrowth).
Early exposure to a range of bacteria in a less sanitised environment helps to improve the ‘tone’ of our gut bacteria and reduces our chance of developing autoimmune issues.
While Dr Ruscio is cautious to highlight that we can’t just run a test and treat based on the results, he does a great job of teasing out what we can really know from the latest research on gut health in his AHS2014 talk.
total or net carbohydrates?
Prebiotics are, quite simply, indigestible food ingredients that stimulate the growth and maintenance of beneficial gut microbiota.
While prebiotic fibre appears to be beneficial for the gut microbiome, some people in the low carbohydrate scene will avoid fibre containing foods to eliminate the risk of these foods impacting on their blood glucose levels.  
In practice, however, this approach leaves people with a fibre intake well below the recommended minimum of 25g for women and 30g per day for men.
In his article Sorry Low Carbers Your Microbiome is Just Not that Into You Jeff Leach of the Human Food Project notes that (although he eats a high fat high fibre diet) people consuming a low carbohydrate diet aren’t necessarily slimmer. He suggests that this may be due to the lack of fermentable fibre.
The confusion around whether to count ‘total carbs’ or ‘net carbs’ is exacerbated by the fact that many people find that, despite claims of low net carbohydrates and high fibre, some manufactured ‘low carb’ products will often raise blood glucose levels.
At the same time, the food insulin index data suggests that there is no insulin response to fibre in foods. As detailed in this article, the correlation between insulin response and net carbs is much better than with total carbohydrates. This makes sense when we consider that fibre is not digested and absorbed by our intestinal tract but is instead metabolized by our gut bacteria.
The formula below for the calculation of insulin load is based on the observation that there is no insulin response to fibre and thus fibre should be negated from the calculation. To minimise the insulin load of our diet we need to prioritise foods that are high in fibre, low in digestible carbohydrates, and moderate in protein.
For most people this is largely a theoretical issue, but for people with type 1 diabetes who need to accurately calculate their insulin dose it becomes more important. The most prudent approach used by experienced type 1’s is to take a ‘net carbs’ approach to real whole foods, while assuming half or maybe all of the fibre in manufactured food products will be digestible (or ideally avoiding manufactured foods completely).
If you are particularly concerned about your blood glucose levels the ideal approach is to do your own n=1 experiment to test and track your own blood glucose levels to see if they rise after a particular food.
Dr David Perlmutter is a fascinating character on the cutting edge of the latest in health and wellness.
Perlmutter talks a lot about the benefits of prebiotics and probiotics for gut and brain health. Prebiotics are fibres that are not digestible by our stomach but rather feed the bacteria in our gut. Probiotics involve actually ingesting bacteria such as those found in yogurt, sauerkraut, Kombucha, Kefir, or other fermented foods.
Perlmutter notes that Americans typically get about five grams of fibre per day compared to the estimated one hundred and thirty grams of fibre that our Palaeolithic ancestors appear to have consumed.
Dr Perlmutter spoke recently on Mark Sisson’s Primal Blueprint podcast about how he believed that type 2 diabetes relates to changes in the gut bacteria and noted that this condition has been reversed through faecal transplants, which transfers healthy gut bacteria from one person into another.
Perlmutter promotes foods high in inulin to feed the gut bacteria. Unfortunately, the issue for people with carbohydrate intolerance is that many of these foods are high in digestible carbohydrates that may also drive their blood glucose levels up.
I thought it would be useful to combine Perlmutter’s list of high inulin foods with an evaluation of their proportion of insulinogenic calories and nutrient density.
As shown in the table below, the highest weighting used in the multi-criteria ranking is given to the insulinogenic properties of the foods (i.e. in order to prioritise foods that will not raise blood glucose levels), with some weighting given to fibre per calorie and fibre per weight, then to nutrient density per calorie and nutrient density per weight, and then calories per weight.
I find that it is important to consider the nutrient and fibre density in terms of both weight and calories. Considering calories alone will bias towards leafy veggies and herbs while considering weight will bias towards nuts and seeds. The best approach seems to be to consider both to get a balance.
|ND / cal||ND / weight||fibre / cal||fibre / weight||calories / 100g||insulinogenic (%)||total|
Shown below are Perlmutter’s recommended probiotic foods from his Brain Maker book sorted based on their insulinogenic properties, fibre content per calorie and nutrient density. The foods with the lowest percentage of insulinogenic calories will have the lowest effect on blood glucose levels. You can see more detail of the analysis here.
|name||% insulinogenic||fibre (g) / kcal||fibre (g) / 100g|
It’s worth noting that Perlmutter generally recommends eating these foods raw. As detailed in this article, cooking will change the fibre content of the foods, but perhaps not as much as you might think.
Limiting FODMAP foods (i.e. Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) is a way of improving digestion in those with irritable bowel syndrome (IBS). However, eliminating FODMAP foods may not be ideal in the long term. Once you have digestive issues under control it may be beneficial to slowly reintroduce FODMAP foods to promote a more diverse bacteria as well as increasing your nutrients.
After a period of avoiding FODMAP foods, the overgrowth of undesirable gut bacteria should diminish and you may be able to tolerate small amounts introduced slowly.
In order to understand which FODMAP foods contain the most fibre and would be gentlest on blood glucose levels, I have run the FODMAP foods through the multi-criteria analysis with the weightings shown above. A shortlist of the highest ranking FODMAP foods is shown below. You can download the full detailed list here.
|name||% insulinogenic||fibre(g) / kcal||fibre (g) / 100g|
Personally, I can eat pretty much anything and not have it bother me. However, I know that eating nutrient dense foods with a lower insulin load has helped me to feel brighter, less inflamed, and less fat.
On the other end of the spectrum, my wife Monica has type 1 diabetes and a host of digestive issues that seem to be part of the autoimmunity package deal. For her, feeling good, getting enough rest, having good gut health, and staying on top of her health is a constant battle.
I’ve been banging on about low carb diets for a while, but Monica’s ability to increase the amount of fat in her diet has been limited. Whenever she’d have a high fat meal she would end up with stomach distress with the same situation occurring with anything that was meant to be ‘helpful’ for the gut like resistant starch, MCT oil or glucomannan.
Late last year we found an excellent naturopath, Elizma Lambert from Realize Health, who was able to identify from her symptoms and testing that she had small intestinal bacterial overgrowth (SIBO) which was stopping her from being able to digest the fats that were critical to succeeding on a low carbohydrate diet.
Elizma was able to guide Moni through a process of cleansing the small intestine and then repopulating it with a diverse range of good bacteria. After testing her faecal microbiota through the Bioscreen lab in Melbourne Elizma was able to identify areas where there was an overgrowth that needed to be treated followed by re-population with a diverse range of new good bacteria.
Individuals suffering from diabetes often struggle to metabolise fats and she also helped her, through supplementation of L-carnitine, to get her fat metabolism moving which has also enabled her to better clear the LDL cholesterol in her blood. Once the digestion and blood glucose levels improved, her depression also lifted and she was able to decrease medications.
More recently however Moni had to have antibiotics for an infection. Unfortunately, the antibiotics also blew away the newly established good gut bacteria for a while, and a lot of the gut distress and depression issues regressed and she has had to work again to rebuild the good gut bacteria.
We’re blessed to have Elizma just around the corner from us in Brisbane Australia, however if you’re dealing with autoimmune or digestive issues then I encourage you to find someone who can guide you through the process, or even contact Elizma directly as she is now able to do consults via Skype. Similarly, Chris Kelly of Nourish Balance Thrive in California, United States, will be able to guide you through the minefield back to metabolic health.
Jimmy Moore’s n=1
I’ve got a lot of time for prolific podcaster Jimmy Moore. I have learned a great deal from his eager pursuit of information from all the experts that he interviews on his show. After a life of morbid obesity, his brother dying at 41, and both grandfathers dying in their early 50s, Jimmy is on a quest to improve his own health and share his journey and learnings with the world in the process.
Jimmy did a very public n=1 ketosis experiment where he lost 78 pounds (35kg) over a year of eating to optimise his blood glucose and maintain nutritional ketosis. Launching from this he wrote the books Cholesterol Clarity and Keto Clarity which has done a lot to increase the profile of the ketogenic diet in the public consciousness.
More recently however Jimmy has struggled to keep the weight off and blood glucose levels down in spite of continuing with a high fat ketogenic diet and keeping his calories reasonably low. Jimmy has been quite up-front about this, even sharing all his test data and two podcast interviews with Chris Kelly of Nourish Balance Thrive.
In the first interview Chris recommended that Jimmy get into a regular exercise routine, eat more veggies, and stop donating blood due to his low iron levels.
After his interview with Chris, Jimmy’s Facebook and Instagram accounts started showing a lot of great looking plates of food piled with heaps of colourful veggies under the hashtag #howIreallyeat.
It seemed that Jimmy has moved on from his position of minimising total carbohydrates to maintain ketosis in favour of maximising veggies and nutrient density.
In their second interview Chris discussed Jimmy’s gut bacteria and possible overuse of dairy, and noted that Jimmy had a particularly limited population of gut bacteria.
Chris: And it’s very unusual for me to see what I saw on your test result, Jimmy, which is really low levels of all of the markers that come from bacteria. I wouldn’t like to say for sure that this means that there’s no bacteria there or undergrowth or anything like that. Again, I think it’s definitely — Once you seen this, it’s worth doing the experiment especially since I’ve seen on the CHRON-O-Meter results that your fibre was only a third of what the RDA is.
Jimmy: It’s higher now.
It seems that after finding that he was not keeping the weight off with the very high fat ketogenic approach that had helped him initially, he was eager to listen to Chris and try more nutrient dense veggies and fibre. Chris Kelly himself eats a very high fat ketogenic diet, but at the same time manages to get very high levels of fibre and nutrient density as detailed in this article.
It’s hard to know if Jimmy’s limited diversity of gut bacteria is the reason for his lifelong struggle with obesity or if it has more recently been exacerbated by his restricted palette of high fat foods low in prebiotic fibre. Jimmy is not the first person I have seen struggle to balance their blood glucose levels in spite of following a disciplined high fat ketogenic diet.
Is Jimmy’s apparent limited microbial diversity due to years of poor nutrition before he found low carb, something weird in the water in North Carolina, or his prolonged extreme high fat diet? Whatever the case, I think Jimmy would do well to take Chris’ advice and continue with his diet heavy in non-starchy veggies that look very tasty, nutrient dense and full of fibre.
Diabetes is a complex disease; however, it seems that gut health and fibre are part of the puzzle.
what does the research say?
I went looking for studies that support the idea that, as suggested by Dr Ruscio, a high fat diet can cause leaky gut and insulin resistance and found a handful of moderately useful references.
- An article by Jamie Scott referenced a study where they found that people on a diet high in omega-6 rich seed oils developed leaky gut, however people on saturated fats fared much better.
- A rodent study from Thomas Seyfried suggested that a diet with excess calories and ketogenic macros can lead to weight gain and poor blood glucose outcomes. However it’s worth noting that the food being tested in the experiment was a high fat powdered formula medical food. It’s hard to know if you would get the same results whole foods.
- In Episode 65 of Tim Ferris’s podcast Peter Attia talks about how he sees some people not thriving on a ketogenic diet, particularly if there is not an energy deficit.
- The study A High-Fat Diet Is Associated With Endotoxemia That Originates From the Gut compares a ‘prudent diet’ (20% fat, 60% carbs, 31g fibre) with the ‘western diet’ (40% fat, 40% carbs and 12.5g fibre) for a month and finds that plasma endotoxin activity increases on the ‘western diet’ compared to the ‘prudent diet’. There are no further details of the diets, however given the difference in fiber it is likely that the ‘prudent diet’ was loaded with veggies while the ‘western diet’ was processed carbs. I think it’s hard to draw any meaningful conclusions from this other than more fiber is better than less fiber, particularly given that 40% fat is not really a high fat low carbohydrate diet.
- The study Comparative effects of very low-carbohydrate, high-fat and high carbohydrate, low-fat weight-loss diets on bowel habit and faecal short-chain fatty acids and bacterial populations compares a low carbohydrate high fat diet (5% carbs, 13g fibre) with a high carbohydrate high fibre diet (including high fibre bran cereal and lentils) (46.4% carbs, 31.5g fibre) and found that the low carb diet group had less butyrate and bifidobacteria than the higher carbohydrate group.
- A range of papers suggest high fat foods lead to metabolic disorders via the mechanism described graphically below.  I’m far from an expert in this emerging field of research, however it appears to me that the mechanism is more likely to relate to the lack of fibre and nutrients rather than necessarily the presence of fat in the diet.
Overall, I would say that research in this area is interesting but not clear cut and subject to prejudice (i.e. people just ‘know’ that high fat diets are bad for you) and bias (e.g. an experiment where the ‘prudent diet’ is full of nutrient dense veggies and fibre while the high fat approach is nutritionally limp by comparison).
Paleo ambassadors such as Chris Kresser, and Robb Wolf have been getting excited lately about a paper by Ian Spreadbury Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity. ‘Acellular carbohydrates’ refers to carbohydrates that are not contained within cellular storage vacules. This includes cereal grains and flours, whereas roots and tubers contain starch within cells (cellular). The title of the paper pretty much says it all.
The paper makes a lot of sense, however what is missing is the ability to quantify ‘acellular carbohydrate’. If we were to try to tie this back to something quantifiable I would say fibre is good, while processed non-fibrous carbohydrates are bad.
My takeaway learnings from the research is that:
- For whatever reason, some people don’t do well long term on an extreme high fat approach.
- Omega-3 fats are better when it comes to gut and metabolic health compared to omega-6 polyunsaturated fats.
- A hypocaloric ketogenic diet is better than a hypercaloric ketogenic diet.
- More fibre is better than less fibre unless you are recovering from digestive issues such as SIBO or IBS. Reducing fermentable fibre is a temporary solution until the yeasts or bacteria are cleared from the small intestine, and in no way a long-term approach to a healthy diet and biochemistry.
From an evolutionary point of view I cannot see a mechanism that demonstrates how naturally occurring fats that we have been eating for many generations (e.g. olive oil, butter, coconut oil, cream, etc.) have suddenly become the cause of the gut distress and autoimmunity that we have seen flourish in recent decades when the use of sugar and highly processed grains have also exploded.
According to Wikipedia:
Butyrates are important as food for cells lining the mammalian colon (colonocytes). Without butyrates for energy, colon cells undergo autophagy (self-digestion) and die.
Short-chain fatty acids, which include butyrate, are produced by beneficial colonic bacteria (probiotics) that feed on, or ferment prebiotics, which are plant products that contain adequate amounts of dietary fibre.
These short-chain fatty acids benefit the colonocytes by increasing energy production and cell proliferation and may protect against colon cancer.
There have been two recent health fads which attempt to increase butyrate:
- resistant starch, and
- Bulletproof coffee.
Increasing the amount of resistant starch in the diet, as promoted by Richard Nikoley and Tim ‘Tater Tot’ Steele, aims to actively feed the good gut bacteria and increase butyrate in the gut from the bacterial fermentation of the resistant starch. Robb Wolf’s sensitive digestion seems to have benefited from adding resistant starch. Mark Sisson also came out with a definitive guide to resistant starch that was overall in favour of it.
Personally I’ve tried resistant starch. It definitely does something in your gut. I can’t say that my life was changed markedly for the better, but it may be a useful supplement. Though as with all supplements, it’s probably not ideal to be taking them for the rest of your life but rather find the required nutrients in real whole food if possible.
One of the claimed benefits of Bulletproof coffee is that high butyrate content of the grass-fed butter is beneficial for the gut. What is not clear though is whether the ingested butyrate actually gets to the lower intestine, as it is a small molecule which would likely be absorbed before it reaches the large intestine. Using butyrate as a suppository or part of an enema is an option, but it seems a better idea to have the colonic bacteria present to produce butyrate and other short chain fatty acids for gut health.
Paul Jaminet is a proponent of safe starches to improve gut health. In his Perfect Health Diet he recommends eating some carbohydrate foods such as white rice, white potato, and sweet potato.
These minimally processed whole foods are better than processed carbohydrate and I can understand how these safe starches could be beneficial to feed gut bacteria, which may lead to an overall improvement in health. However, for a diabetic these high GI and high carbohydrate foods likely do not provide an acceptable solution when it comes to blood glucose levels.
sugar, processed carbohydrates and gut health
It seems most people agree that that cutting out sugar and processed foods is a good thing.
Dropping sugar and processed carbohydrates will reduce your chance of feeding an overgrowth of ‘bad bacteria’ (especially Streptococcus, Enterococcus and yeasts such as Candida albicans).
fibre and satiety
Fibre makes us feel full. While high fat foods are calorie dense (at nine calories per gram), high fibre foods increase the bulk of our food without necessarily increasing calories.
Glucomannan is a water soluble dietary fibre with some clear research findings behind it, showing that it absorbs water and swells in your stomach to promote a feeling of fullness, as well as working as a prebiotic to increase the diversity of bacteria in the gut.
The other good thing about high fibre foods is that they often come packaged with plenty of nutrients.
Real whole foods will be more likely to contain the essential nutrients, as well as other beneficial nutrients that we have not yet identified. Isn’t the ideal food something that will give us plenty of fibre to feed our gut, keep us full, give us nutrients and keep us regular?
While there are lots of fibre supplements out there (e.g. glucomannnan, potato starch, and psyllium husk) I think the ideal way is to maximise the nutrient dense high fibre foods.
In line with the idea that we want to promote a good range of healthy gut bacteria, we also want to eat a wide range of fibre in our food (soluble, insoluble and mucilaginous) to promote a wide range of gut bacteria.
so how do we get fibre without raising blood sugars?
Again, we seem to have a balancing act between maximising fibre and nutrition on one hand and managing blood glucose levels on the other.
So what foods can we eat that will give us all the good stuff without negatively impacting our blood glucose levels?
Rather than just looking at high inulin foods or FODMAP foods as discussed above, I have analysed all of the USDA foods database to find the foods that have the highest amount of fibre that will provide us with plenty of nutrients and be gentle on our blood glucose levels.
The highest ranking foods are shown below while a more extensive list can be downloaded here (note: this list is sorted based using a multi criteria analysis that considers fibre, nutrient density and insulinogenic properties). Foods with a lower percentage of insulinogenic calories will be gentler on your blood glucose levels while the foods with more fibre will be great for your gut.
As you look down this list you will see that most of these foods are nutrient dense seeds, herbs or leafy vegetables. Rice and wheat feature in the mix, but only in their natural unprocessed form.
|food||% insulinogenic||fibre (g) / kcal||fibre (g) / 100g|
|Kellogg’s all-bran w/ ex fibre||35%||0.13||50|
|sesame butter (tahini)||18%||0.02||9|
|pepper, red or cayenne||34%||0.06||27|
As shown in the formula below the percentage of insulinogenic calories is lower the more fibre we have.
If you are concerned about your blood sugar then try to choose foods with a lower percentage of insulinogenic calories, keeping in mind that a whole egg is about 25%.
In summary, I think a ‘well formulated ketogenic diet’ that will be beneficial for both blood glucose and overall health.
A high fibre nutrient dense diet will give you a better chance of achieving health without messing up your blood glucose levels.
- Thanks to Alex Leaf and Elizma Lambert of Realize Health for reviewing this article and providing some of the more technical detail. If you feel like you’ve tried everything and still need some help I highly recommend contacting Elizma who can arrange some additional testing and get to the bottom of the issue.
- Thanks to Jimmy Moore for chasing Dr Ruscio for some more references on the subject and Michael Ruscio for providing references.