This morning, the English language newspaper, the Montreal Gazette published a special article written by Dr. Joe Schwarcz, Professor of chemistry from McGill University titled “The Right Chemistry: Keto diets work, but is there a catch?”, that had an accompanying video.
The 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 titled Misconceptions About the Keto Diet;
“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;
(1) avoids bread, pasta, cereal, potatoes, carrots, rice, fruit* or beer
(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.”
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”
Correctly the article 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 my 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).
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.
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To your good health!
UPDATE (February 15, 2019): a review of Dr. Schwarcz' follow up to this article is located here.
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- Dr. Joe Schwarcz, “The Right Chemistry: Keto diets work, but is there a catch?” Montreal Gazette, February 8, 2019, https://montrealgazette.com/opinion/columnists/the-right-chemistry-keto-diets-work-but-is-there-a-catch