The plant-based diet bias in criticising LCHF: Katz and co


Drs David Katz and Garth Davis are a good example of the type of crypto-vegan medical professional who believe in the power of the “plant based diet”. They have a knee jerk reaction to low carb diets, because they think these involve eating more meat.

Here’s a news flash – you can eat more meat on a low carb diet (because who knows if you ate any before), but you don’t need to, and you may well eat less, just because you’ll probably be eating less anyway, without much effort. …And LCHF well formulated is a high plant diet.

Newsflash 2: Cereals aren’t plants. They are highly processed foods made in factories.

Newsflash 3: You can eat a plant-based diet and be LCHF if you want.

But there’s more to it than just these revelations. There is a deeper unscientific criticism of LCHF, from scientists, which needs to be uncovered. Here it is.

They presented a blog on the Very Well website, a health and lifestyle platform which has also run more positive articles about LCHF, that’s critical of Drs Sarah Hallberg and Osama Hamdy’s recent opinion piece in the New York times saying that LCHF diets can be a viable alternative to bariatric surgery for diabetes.

Katz is from Yale (see his www site), and in our view is a “fence sitter” who criticises LCHF and other approaches which should be given as an option.

Katz introduces Davis, who then makes some numbered points. In our opinion these are all off the mark, and the condemnations of LCHF in particular include pseudoscientific scare stories; the sort of things that plant-based diet advocates fear will happen to them if they stop eating wholegrain cereals, but for which there is absolutely no evidence at all.

1. The authors imply that weight loss surgery is not effective.

Nowhere in the NYT article was it implied that bariatric surgery is ineffective.

In fact, though any surgery carries both a risk and a hefty price tag, there is good evidence that some forms of bariatric surgery are effective at reducing weight and reversing diabetes. Garth Davis, who is a bariatric surgeon, says “I see 80 percent to 85 percent of my gastric bypass patients off their diabetic medications five years later”, and this is a good result. Unless you are one of the other 15-20% (which is it?), some of whom may well have undergone a much bigger commitment than dieting for no improvement.

Dr Davis says “Long-term side effects of low-carb dieting may include high cholesterol, cardiovascular disease, kidney stones, bone loss, erectile dysfunction, malnutrition, and an increased risk of cancer.”

We have never heard of most of these; cholesterol usually goes down (if it’s high), it can sometimes go up, but there’s no evidence that rises in cholesterol related to carbohydrate restriction increase cardiovascular disease, and reason to think that they are at worst neutral. Why you would experience bone loss on any well-formulated diet, we can’t begin to think, but again there’s no record of this happening. A 24-month study of the Atkins diet found no new cases of kidney stones, and no change in bone density (in any case, these concerns belong to very high protein diets).[1] As with erectile dysfunction; there’s no data on this either, but all these U.S. plant-based dudes seem to be very defensive about virility, maybe because of the scare stories about soy isoflavones. Malnutrition? That’s up to your dietitian, surely, but if you eat real food and mix up a good variety of animals and vegetables you can’t go wrong.
Cancer, of course, is the big scare story. We all know we’ll get cancer if we eat red meat or forget to eat our wholegrain fibres. Unfortunately there’s no good evidence for this. Diabetes (defined by high blood sugar) increases the risk of every cancer except prostate cancer, and a higher HDL level is associated with reduced risk, showing an obvious point at which diet influences risk. Ketogenic diets have actually shown promise for reducing cancer growth in early research.

As for meat, there is an interesting finding from the EPIC-Oxford study. It was a study of “health conscious” individuals (i.e. with less confounding from unhealthy behaviours), and in this population, which had a low mortality rate overall, vegetarians had a significantly higher rate of colorectal cancer than meat eaters.
“The incidence rate ratio for colorectal cancer in vegetarians compared with meat eaters was 1.39 (95% CI: 1.01, 1.91).“ [2]

Garth Davis fails to list the long-term side effects of bariatric surgery. Unlike the long-term low-carb diet side effects listed, these are not imaginary or conjectural but a matter of medical record. For example (these are just some listed)

Nutritional deficiencies are a common after-effect of surgery.

Between 13% and 36% of patients develop cholesterol gallstones after surgery, due to rapid weight loss, but only 10% develop symptoms requiring surgical intervention. (cholesterol gallstones are  a common side-effect of rapid weight loss on low-fat diets, but not LCHF diets).

8% to 10% of patients developed incisional hernias after open bariatric surgery.

Less than 5% to 10% of patients have chronic problems with dumping syndrome, which can cause facial flushing, lightheadedness and diarrhoea after eating carbohydrate-rich meals. Most patients find that reducing their intake of carbohydrates and avoiding drinking liquids half an hour before and after eating improves their symptoms.[3]

So some common side effects of bariatric surgery can be lessened or avoided by restricting carbs after surgery. Maybe this also helps to explain why 80-85% of Dr Davis’s patients can remain free of diabetes medications. These side effects are more common than the supposed serious side effects of LCHF, which have not been reported in RCTs, so we can’t even put a % figure on them.

2. They assume that patients who see bariatric surgeons have never tried dieting endlessly and over all types of diet before.

In fact, all of our practice’s patients have tried weight loss diets, multiple times. Many have dieted since “fat camps” as children. The number one diet our patients attempt is the Atkins diet (a popular low-carb approach), often numerous times, resulting in a fear of carbohydrates.
Nobody goes into surgery without having given a valiant effort at dieting. For many insurance companies, preoperative attempts at dieting are mandatory, and I know very few surgeons who would operate on a patient that has never tried to lose weight before.

If you go to a bariatric surgeon to reverse diabetes, clearly you have a serious medical problem. You want to be dieting in a way that’s supported and encouraged by your health providers. This is unlikely at present to be the Atkins diet (which can mean a number of different low carb approaches, including diets high in processed foods, or high in protein). Garth Davis plainly doesn’t support the LCHF approach, so his testimony about it can only be second-hand and anecdotal. Why might the “Atkins” diet fail these patients? There’s a clue in the recent Fat vs Carbs documentary on Welsh BBC TV. Presenter Jamie Owen goes on the LCHF diet to lose weight (it works, and his cholesterol goes down). Before he starts, his GP and the dietitian consulted say that he should follow it for “no longer than 3 weeks”. Really?

If you’re not supported in your efforts long-term, if you have “experts” sniping from the sidelines about cancer risk this and bone loss that, it takes a stubborn person to get good long-term results. Dr Sarah Hallberg, on the other hand, supports her type 2 diabetes patients to follow the LCHF diet, as does Dr David Unwin in the UK, and their patients don’t have a high failure rate at all. Plainly, if you do LCHF differently, you can get different results.

The bariatric surgeon is the ambulance at the bottom of the cliff. All other objections aside, it would be impossible to treat every case of diabetes by this method, no matter how effective.

3. The authors reveal a lack of knowledge as to the root mechanism that causes diabetes.

They seem to assume that diabetes is simply a result of high blood sugar, when in fact the high sugar is the symptom, not the cause, of diabetes. Lower carbohydrate intake will drop blood sugar, but it does not address the central issue—the body is no longer able to process the carbs.

In reality, diabetes is caused by uptake of fat into muscle and liver cells. This greatly impedes the body’s ability to make insulin receptors, and without insulin receptors, sugar cannot get into the cell. The low-carb diet will lower blood sugar, but it will not fix the underlying problem of insulin resistance.

Here, it is Davis and Katz who shows poor understanding of mechanisms. High carbohydrate intakes in people with type 2 diabetes push insulin high, and insulin is what governs the accumulation of fat in the body, including in muscle and liver (and pancreas) resulting in insulin resistance (insulin itself downregulates the insulin receptor if present in excess). On a very low carbohydrate diet, insulin drops and this fat is released and oxidised, restoring insulin sensitivity. Very low carb diets are highly effective for reducing liver fat (a bariatric surgeon should know this).[4]
Sugar can get into cells without insulin receptors – glucose uptake is not the main problem in diabetes – instead, insulin resistance means that the liver doesn’t stop releasing glucose when you eat carbs. It’s the failure of insulin’s inhibitory effect that defines diabetes and results in high blood glucose.[5]

The effects of this ‘black age’ are still with us because these incorrect hypotheses have, with the passage of time, been turned into dogma and become cast into ‘tablets of stone’ in undergraduate textbooks. They are also carried forward into postgraduate teaching. For example, even in well respected texts it is still common to find statements such as ‘The basic action of insulin is to facilitate glucose entry into cells, primarily skeletal muscle and hepatocytes.’ – Sonksen and Sonksen [5]

4. They suggest that the low-carb diet was the favored and only diet for diabetes until recently.

This is just false. In fact, at Duke University in the 1940s, Walter Kempner, MD, treated diabetes successfully with the Rice Diet.

Randomized clinical trials beginning in 1976 collectively highlight the efficacy of a plant-based diet in diabetes management. And recent studies funded by the National Institutes of Health (NIH) have shown us that plant-based diets are even more effective than the traditional American Diabetes Association (ADA) diet plan. As a result, the ADA includes plant-based eating patterns as a meal-planning option in their nutrition recommendations for people with diabetes.

In fact, Davis is distorting history here. The rice diet was never mainstream, and in any case was a highly restrictive inpatient diet, whereas pre-insulin LCHF diets like the Michigan Diet were designed to support patients with enough energy to stay active and keep working.[6]
It doesn’t surprise us that plant-based diets are more effective than the ADA diet plan. As far as we know, every therapeutic diet that has ever been tested has been shown to be more effective than the ADA diet plan. Replacing refined carbs and denatured fats with their equivalents in real foods, even in plant form, is obviously going to slow the appearance of glucose in the blood and lower elevated insulin. That’s why the LCHF diet includes lots of non-starchy vegetables, low-sugar fruits, and fatty fruits and nuts. It’s often a plant-based diet too, if by that is meant a diet high in unprocessed plant food by volume.

Fifth: The authors insinuate that low-carb diets have somehow been erroneously abandoned and should be brought back.

The idea is that low-carb diets worked but the “low fat craze” prematurely, and inappropriately, ended the popularity of the low-carb diet. Low-carb diets have been around since the 1800s.  There have been numerous best-selling books through the years touting low-carb dieting as the holy grail. Yet, the diet has repeatedly fallen out of favor, not because of some low fat conspiracy, but because side effects have kept it from being utilized long term.

One might ask, where is the rice diet now? Does anyone at all still use it?

In any case, this is not the reason the low-carb diet fell from favour. Its use declined in diabetes treatment because the mass-production of insulin made it seem unnecessary; its use for weight control declined after the 1960s for the reasons Dr David Ludwig gives in his recent JAMA article, and this – with very little testing, and no testing at all of the very low-carb diet – further.influenced diabetes recommendations.[7,8] After which time obesity and diabetes really did take off – if dietary treatment of these conditions had actually improved in the low-fat, low-animal fat era, this would probably not have happened.

Dr Sarah Hallberg and others are using the LCHF diet on an increasingly large scale and making it work for their patients. Instead of attacking them (and the real reason for this here seems to be opposition to the inclusion of animal foods and animal fats in the diet), why not study what they’re doing right? Hint: it involves including enough real foods – fatty animal foods and low carb vegetable foods – that people don’t feel deprived and persist in the diet long enough to adapt to it. It becomes a way of life – or, at least, a way of eating – that promotes health and enjoyment, and not a crash diet or another fad.

Telling a morbidly obese patient with diabetes to go on yet another low-carb diet is a form of fat shaming and is completely inappropriate management of this disease.
My suggestion to patients dealing with obesity and diabetes is to eat a predominantly whole foods, plant-based diet and to exercise.

Huh? Come again? The other guy’s diet advice is automatically fat-shaming, but your advice to eat virtuously and exercise (I bet they’ve never heard that before) isn’t?


[1] Friedman AN, Ogden LG, Foster GD et al. Comparative Effects of Low-Carbohydrate High-Protein Versus Low-Fat Diets on the Kidney. Clin J Am Soc Nephrol. 2012 Jul; 7(7): 1103–1111.

[2] Key TJ, Appleby PN, Spencer EA et al. Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009 May;89(5):1620S-1626S. doi: 10.3945/ajcn.2009.26736M. [link]

[3] Hamdan K, Somers S, Chand M. Management of late postoperative complications of bariatric surgery. Br J Surg. 2011 Oct;98(10):1345-55. doi: 10.1002/bjs.7568.

[4] Browning JD, Baker JA, Rogers T et al. Short-term weight loss and hepatic triglyceride reduction: evidence of a metabolic advantage with dietary carbohydrate restriction. Am J Clin Nutr. 2011 May;93(5):1048-52. doi: 10.3945/ajcn.110.007674. Epub 2011 Mar 2.

[5] Sonksen P, Sonksen J. Insulin: understanding its action in health and disease. Br. J. Anaesth. (2000) 85 (1): 6979 doi:10.1093/bja/85.1.69

[6] Henderson G. Court of Last Appeal – The Early History of the High-fat Diet for Diabetes.  J Diabetes Metab. 2016; 7:696. doi: 10.4172/2155-6156.100696

[7] Ludwig DS. Lowering the Bar on the Low-Fat Diet. JAMA. Published online September 28, 2016. doi:10.1001/jama.2016.15473

[8] Schofield GM, Henderson G, Thornley S. Very low-carbohydrate diets in the management of diabetes revisited. N Z Med J. 2016 Apr 1;129(1432):67-74.

8 Comments on “The plant-based diet bias in criticising LCHF: Katz and co

  1. Thanks for your excellent comments, pointing out the many errors in the Very Well blog article. It is not surprising that a weight loss surgeon is going to mis-represent the facts about LCHF diets. For me Garth Davis, MD completely loses all credibility when he states that the rising rates of diabetes in China and other Asian countries are “because of the meat that is becoming more central in the diet”
    I am a GP in Christchurch. I am now routinely recommending LCHF diets to my obese patients if they show signs of metabolic syndrome or type 2 diabetes. It makes sense, now that the fear that saturated fats cause heart disease has been put to rest.
    Chris Leathart

  2. Unlike the conflicted and bombastic Dr Katz,
    Dr Davis seems like a genuinely good guy in his social media interactions; but unfortunately, that doesn’t make his protein hypothesis true.

    “In contrast to hypothesized risk of high protein, we found that for adults 50+ y, low protein intake (below 15% TEI) may lead to increased fracture risk. Source of protein was a determinant of BMD, but not fracture risk.”

    Langsetmo L, Barr SI, Berger C, Kreiger N, Rahme E, Adachi JD, Papaioannou A, Kaiser SM, Prior JC, Hanley DA, Kovacs CS, Josse RG, Goltzman D; CaMos Research Group.
    Associations of Protein Intake and Protein Source with Bone Mineral Density and Fracture Risk: A Population-Based Cohort Study.
    J Nutr Health Aging. 2015 Oct;19(8):861-8. doi: 10.1007/s12603-015-0544-6.

  3. Nice rebuttal. Katz is a self aggrandizing douche-bag. I wasn’t surprised to find out that his Yale health clinic (or whatever it is called) while giving the impression of being associated with the prestigious university – it is not, it just shares the name. The sort of legal yet slimy marketing that Katz uses to further his brand.

  4. I’m a liberal American T1D. So, I read the Huffington Post, especially the Heath section. Dr. Katz writes articles for them. I’ve written many comments trying to expose all of his double speak, straw man arguments, misrepresented data, and his statements that his advice is truthful and honest while others’ is not. Huh? Why?

    • Hi Jack,

      FMD is an effect of insulin in response to glucose that adjusts blood flow to the extent needed to make glucose available to cells, of course it’s reduced when the diet is low in carbs, the mechanism is outlined here

      If you are insulin-resistant and eating excess carbohydrate, the vessel doesn’t dilate when it should, only one of many problems in that scenario.
      We see people reporting zero CAC scores after years on LCHF, a good sign that CVD is not being promoted when insulin is kept low.

    • Hi Jack,

      you might like this study

      A 21 day Daniel Fast improves selected biomarkers of antioxidant status and oxidative stress in men and women
      Richard J Bloomer, Mohammad M Kabir, John F Trepanowski, Robert E Canale and Tyler M Farney
      Nutrition & Metabolism 2011;8(17) DOI: 10.1186/1743-7075-8-17

      “Also of interest, we noted similar mean changes between vegetarians and omnivores in our sampled biomarkers. For example, the six vegetarian subjects in our study experienced a 10% reduction in MDA and a 79% increase in NOx from pre to post fast. These results suggest that the exclusion of meat from the diet is not the only dietary factor responsible for altering oxidative stress, antioxidant capacity, or nitric oxide metabolites. It is likely that multiple dietary factors – particularly the exclusion of additives, preservatives, and high-glycemic, processed carbohydrate foods, in addition to the focused inclusion of fresh and frozen fruits and vegetables – positively affected the biochemical variables measured in the present design”.

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