McGill Professor: Risks and Benefits of Low-Carb Keto Diets

INTRODUCTION: Last Friday, February 8, 2019, the Montreal Gazette published a special article with accompanying video by Dr. Joe Schwarcz, Professor of Chemistry from McGill University titled “Keto Diets Work, but is There a Catch?” and this morning the follow-up was published titled “The Known Benefits of Low-Carb Keto Diets”. This post contains a summary of both.

PART I – “Keto Diets Work, but is There a Catch?”

Dr. Joe Schwarcz, The Montreal Gazette, February 8, 2019 (reference below)

This article began;

“There is little doubt that cutting way back on carbs results in weight loss. But how does all that fat impact cardiovascular risk factors?”

This is a very good question, however it is incorrectly based on the assumption that a “keto diet” is necessarily very high in fat, especially saturated fat, something which is not necessarily the case.

Dr. Schwarcz stated in the article in the Montreal Gazette that on a “keto diet” there is no bread, pasta, cereal, potatoes, carrots, rice, fruit or beer but that one can;

“gorge on fish, butter, eggs, high-fat cheese, whipped cream, coconut oil and meat to your heart’s delight.”

As mentioned in an earlier article that I wrote on a site dedicated to low carbohydrate diets;

“There is no one “keto diet“, but many variations of ketogenic diets that are used for different therapeutic purposes.

Some therapeutic ketogenic diets are used in the treatment of epilepsy and seizure disorder and are extremely high in fat. Other types of therapeutic ketogenic diets are used in the treatment of various forms of cancer (those that feed on glucose), such as brain cancer. There are ketogenic diets that are used in the treatment of Polycystic Ovarian Syndrome  (PCOS), as well as for weight loss and for increasing insulin sensitivity in those with Type 2 Diabetes and insulin resistance.

Even among those using a nutritional ketogenic diet for weight loss and to increase insulin sensitivity, there is no one “keto diet”.

There are ketogenic diets with a higher percentage of fat than protein, with a higher percentage of protein than fat and mixed approaches which may have different ratios of protein to fat – depending on whether the individual is in a weight loss phase or a weight maintenance phase.

There are as many permutations and combinations as there are people following a keto diet for these reasons.

What makes a diet ketogenic (or keto) is that the amount of carbohydrate relative to the amount of protein and fat results in the utilization of fat as a primary fuel source rather than carbohydrate. “

Assuming that the specific type of “keto diet” that Dr. Schwarcz is referring to is one where one that (1) avoids bread, pasta, cereal, potatoes, carrots, rice, fruit* or beer and (2) indulges in foods high in fat, such as fish, butter, eggs, high-fat cheese, whipped cream, coconut oil and meat, it is a very appropriate question to ask as to what effect does this type of keto diet have on cardiovascular risk factors.

Note: Most keto diets used for weight loss allow fruit as berries, such as raspberries, strawberries, blueberries, blackberries as well as those fruit that we often think of as vegetables, including tomato, avocado, cucumbers, lemon and lime.  Dr. Schwarcz raised a concern in the video that not eating fruit limits one’s access to the important antioxidants in fruit, which for the most part is incorrect.

The article states that;

“There is little doubt that cutting way back on carbs results in weight loss. The question is, why?

The body’s main source of energy is glucose, generally supplied by starches and sugars [i.e. carbs] in the diet. If consumption of these carbohydrates is drastically reduced, below about 50 grams a day, energy has to be derived from an alternate source. At first, the 65 or so grams of glucose the body needs per day are produced from amino acids, sourced from proteins. But this process itself has a high energy requirement, and furthermore, the body is not keen on using up proteins that are needed to maintain muscle integrity. Fortunately, there is a backup system that can swing into action.

The liver begins to convert fats into “ketone bodies,” namely beta-hydroxybutyrate, acetoacetate and acetone. These are then shuttled into the mitochondria, the cells’ little energy factories, where they are used as fuel. At this point the body is said to be in “ketosis,” with excess ketones being excreted in the urine.”

Great explanation!

The article raises a few excellent points;

The article states that the “usual argument” for the more efficient weight loss associated with extremely low carb diets as compared to low fat diets is that (1) low carb diets produce a metabolic advantage because a lot of calories are needed to convert proteins to glucose.  The article adds that not everyone agrees with this premise and states that others suggest that (2) ketone bodies have either a direct appetite suppressant effect or that they (3) alter levels of the respective appetite stimulating and inhibiting hormones, ghrelin and leptin. Lastly, the article states that some argue that (4) ketogenic diets lead to a lower calorie intake which the article’s author believes is “due to the greater satiety effect of protein”.

“No long-term studies of keto diets”

The article correctly states that;

“There are numerous studies published over the last 20 years that have compared low-fat diets to low-carb diets with the overall conclusion that the low-carb diets are more effective in terms of weight loss, at least in the short term.

…but incorrectly adds;

“Unfortunately, there are no long-term studies of keto diets.”

While there have been 3 long-term clinical trials (2 years) published over the past 10 years involving low carb diets, unfortunately as documented in and earlier article none of these involved research groups that actually ate a low carbohydrate diet. There is, however the recent two-year data from the Virta Health’s study that was published this past December 2018 which demonstrated the long term safety of a ketogenic diet and that participants on average;

(1) lost 12.4 kg (28 pounds) in two years; most of which was achieved in the first year maintained with only a slight increase of 2.3 kg (5 pounds) in the second year.

In addition to the weight loss, participants in the Virta Health study;

(2) significantly lowered medication use for Type 2 Diabetes (read more here)

(3) lowered glycated hemoglobin (HbA1C) by a full percentage point at two years (7.7% to 6.7%)

(4) lowered fasting blood glucose from 9.1 mmol/L (164 mg/dl) at the start of the study to 7.4 mmol/l (134 mg/dl ) at two years.

High Fat Keto Diet and Cardiovascular Risk Factors

The article concludes with the initial question as to how a diet “high in fat, such as fish, butter, eggs, high-fat cheese, whipped cream, coconut oil and meat” impacts markers of cardiovascular risk.

“As one would expect, LDL, the “bad cholesterol,” does go up, although the increase is mostly in the “large particle” sub fraction that is deemed to be less risky.

Triglycerides, a significant risk factor, actually decrease on a very-low-carbohydrate diet, as does the body’s own production of cholesterol.

Levels of HDL, the “good cholesterol,” increase.

That is, over the short term, markers of cardiovascular risk doesn’t change to any degree.

What about over the long term?

Unfortunately, the article concludes with;

“the problem is that there are no studies of people who have followed a keto diet long enough to note whatever effect such a diet may have on heart disease.”

…but as mentioned above, we do have the two-year data from the Virta Health’s study that was published this past December 2018 and which demonstrates that;

(1)  LDL cholesterol of the intervention group at the start of the study averaged 2.68 mmol/L (103.5 mg/dl) and at two years was slightly higher as expected, to 2.96 mmol/L (114.5 mg/dl), however this level after 2 years was almost identical to what it was at 1 year; 2.95 mmol/L(114 mg/dl). That is, LDL (mostly the large particle sub-fraction) increased as expected the first year but didn’t continue to rise.

(2) At baseline, HDL cholesterol (“good cholesterol”) of the intervention group averaged 1.11 mmol/L (41.8 mg/dl) and after two years was stable at the same level it had risen to at 1 year, namely 1.28 mmol/L (49.5 mg/dl).

(3) At baseline, triglycerides of the intervention group averaged 2.23 mmol/L (197.2 mg/dl) and at two years was down to 1.73 mmol/L (153.3 mg/dl ), only up slightly for the one year average of 1.68 mmol/L (148.9 mg/dl).

Final Thoughts…

While Dr. Schwarcz seemed to be unaware of the publication of the two-year Virta Health study data in December 2018 that demonstrates both long-term safety and efficacy of a ketogenic diet for weight loss and improvement in metabolic health (including markers of cardiovascular risk), the Montreal Gazette article and accompanying video does indicate that a very high fat ketogenic diet does not adversely impact markers of cardiovascular risk.

  1. Dr. Joe Schwarcz, “The Right Chemistry: Keto diets work, but is there a catch?” Montreal Gazette, February 8, 2019,

PART II – “The Known Benefits of Low-Carb Keto Diets”

Dr. Joe Schwarcz, The Montreal Gazette, February 15, 2019 (reference below)

This morning, Dr. Joe Schwarcz, Professor of Chemistry from McGill University and popular radio show host released a follow-up to last week’s opinion article and video that was published in the Montreal Gazette on the cardiovascular risks of a keto diet; this one on the known benefits of low-carb keto diets.

Schwarcz begins by fondly reminiscing about going to the circus with his mother when he was about 7 or 8 years old and the memories of the snack that she packed for him of crusty Hungarian bread, slathered with butter and topped with green bell pepper. He said that he’s loved it ever since, but “now we question such snacks. Why? Because of the carbohydrate content of the bread”.

“I’ve been looking into this for quite a while. There is really a plethora of papers and information that floods us about the keto diets; the very low carbohydrate diets”.

To his credit, Dr. Schwarcz acknowledged (possibly as a result of my written response to his article of last week in the Montreal Gazette) that there isn’t just one “keto diet” (singular) but several very low carbohydrate diets (plural) .

Schwarcz reiterates;

“I would have thought that by having all of that fat in the diet that risk levels for certain cardiovascular factors would go up, but really there isn’t really that much alteration in these factors”.

Low-Carb “Keto” Diets and Diabetes

Transitioning from the lack of cardiovascular risks associated with low-carb keto diets, Schwarcz adds;

“When it comes to Diabetes the information is really overwhelming to the benefit of these low carb diets. There are people — Type 2 Diabetes sufferers, who have been able to give up their medication by following a stringent, low carbohydrate diet.”

Schwarcz dismisses anecdotal reports of people’s “brain fog” resolving and possible benefits for cancer, Parkinson’s disease and Alzheimer’s disease as not being scientifically based but is unequivocal about the known benefits;

“What we do know is that weight loss can be very significant on a low carbohydrate diet and as I said — surprisingly, without any significant risk factors.”

Schwarcz continues;

“On the other hand, the longest terms studies that I’ve seen which were really properly controlled have only been about six months, and that really isn’t long enough.”

NOTE: In this case, Dr. Schwarcz is referring only to randomized, controlled double blind studies — excluding the data from long term studies of other types.

“We also know from dietary studies that after about a year, it doesn’t much matter what diet you’re on when it comes to weight loss — whether it’s low fat, whether it’s low carb, the results tend to be the same as long as you’re cutting out some calories.”

NOTE: While this may be true, what Schwarcz neglects to mention is that the major difference is that in a calorie-restricted low-fat diet, people are deliberately restricting food intake, often feeling hungry — whereas in a low carbohydrate diet, people naturally feel less hungry due to the satiety (hunger-reducing effect of protein and fat) which results in them eating less. In one case people are purposely restricting calories in the the other case, they don’t feel as hungry so they naturally eat less.

Schwarcz reiterates;

“However, for people who are afflicted with Diabetes, I think there is no question that the very low carb diets are worth trying.”

Towards the end of the video Dr. Schwarcz reflects on his childhood snack of crusty Hungarian bread, slathered with butter and topped with a quarter of a green bell pepper and admits that he looks askew at this snack.

“I admit that I’ve been eating less bread — I haven’t cut it out because I don’t think I need to do that, but I’m eating less.”

Schwarcz adds that for those who are gravitating towards a low carbohydrate diet, they can opt instead to eat bell pepper with a dollop of hummus with tahini (ground sesame seeds) or raw broccoli dipped in a bit of hummus.

“It tastes good! I think it is possible to cut down on the bread!”

Since Dr. Schwarcz is presumably not Diabetic and has all the nostalgia of memories of the circus as a child, he concludes the video by happily biting into a slice of crusty Hungarian bread that’s been slathered with butter and topped with a quarter of a green bell pepper…for nostalgia reasons, of course!

Bon appetit, Dr. Schwarcz!

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Montreal Gazette, February 15, 2019, Dr. Joe Schwarcz, Known Benefits of Low Carb “Keto” Diets”

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