Low-carb diets and paleolithic nutrition are all the rage these days, and for good reason. Compared to the Standard American Diet, both of them are superb.
Few of us would dare to take the two to their extreme, however. Giving up sugar and wheat is one thing, but what about giving up everything except meat? Yes, I'm talking about an ultra low-carb diet with even foods like nuts and berries removed. Unsurprisingly and understandably, studies on the long-term effects of such a diet are severely lacking.
There is at least one study that did just this, however. If the diet brings the Eskimos to mind, it's no coincidence. You may have heard of Dr. Vilhjalmur Stefansson - the Canadian ethnologist who spent more than a decade with the Inuit during his arctic explorations in the beginning of the previous century. For nine of these years, he lived almost exclusively on fish and meat (you can read about his experiences here). At the time, this was considered heresy and life-threatening, just as it is today (note that Stefansson apparently refers to both fish and meat with the word "meat"):
A belief I was destined to find crucial in my Arctic work, making the difference between success and failure, life and death, was the view that man cannot live on meat alone. The few doctors and dietitians who thought you could were considered unorthodox if not charlatans. The arguments ranged from metaphysics to chemistry: Man was not intended to be carnivorous - you knew that from examining his teeth, his stomach, and the account of him in the Bible. As mentioned, he would get scurvy if he had no vegetables in meat. The kidneys would be ruined by overwork. There would be protein poisoning and, in general hell to pay.To the surprise of many (including Stefansson himself), he suffered no health problems during his decade of pure carnivorism. When he told people of his amazing experiences, he was met with skepticism from medical authorities who asked him to undertake a study that would replicate the results. He and a fellow explorer named Andersen agreed to eat an all-meat diet for an entire year in a closely observed setting.
Composing a diet of nothing but meat and fat
This time, however, the diet was even more radical than the traditional Eskimo diet, which is based on fish and includes a small amount of berries and vegetables - not a lot, but enough to keep them out of ketosis most of the time. Furthermore, since fish is high in omega-3 fatty acids, you could argue that it's all those good fats that keep the Eskimos free of disease.
But how could anyone subscribing to conventional health wisdom explain thriving on a diet consisting solely of red meat? No vegetables, no fruit, no vitamin supplements. Nothing. Just meat and animal fat.
The results of this fascinating study were published in 1930 in the Journal of the American Medical Association (link). At the beginning of the experiment, Stefansson was given only lean meat at the request of his supervisors. This was to confirm Stefansson's bad experiences with low-fat meat; during his explorations, there had been periods during which fat was not readily available and which lead to diarrhea and nausea in a few weeks. This time, the illness kicked in much earlier:
As said, in the Arctic we had become ill during the second or third fatless week. I now became ill on the second fatless day. The time difference between Bellevue and the Arctic was due no doubt mainly to the existence of a little fat, here and there in our northern caribou - we had eaten the tissue from behind the eyes, we had broken the bones for marrow, and in doing everything we could to get fat we had evidently secured more than we realized. At Bellevue the meat, carefully scrutinized, had been as lean as such muscle tissue can be.After fat was added back into the diet, a full recovery was made in two days. The authors of the study describe the diet from then on:
The meat used included beef, lamb, veal, pork and chicken. The parts used were muscle, liver, kidney, brain, bone marrow, bacon, and fat.Thus, fat played an important part in their diets. According to the authors, Andersen usually ate beef, while Stefansson often chose lamb. Both men ate about 800 grams of meat per day in 3-4 meals. The protein contents ranged from 100 to 140 grams, the fat from 200 to 300 grams, and carbohydrates from 7 to 12 grams. In calories, the percentages were 15-25% protein, 75-85% fat, and 1-2% carbohydrate. The carbs came solely from the glycogen of the meat, making this not so much a low-carb as a no-carb diet. In addition to water, coffee and tea were allowed throughout the period.
Health markers after one year
Examinations at the end of the observation showed that both men were healthy while on the diet. The authors write:
There were no subjective or objective evidences of any loss of physical or mental vigor. The teeth showed no deterioration and gingivitis had disappeared. There was, however, an increase in the deposit of tartar on the teeth of [Stefansson]. Bowel elimination was undisturbed.Though neither man was overweight to begin with, and weight loss was not the goal of the experiment, both men lost a few pounds during the year. This was despite the fact that calorie intakes ranged from 2,000 to 3,100 kcal. Stefansson averaged about 2,650 kcal (2,100 from fat and 550 from protein), while Andersen averaged 2,620 kcal (2,100 from fat and 510 from protein).
Given that Stefansson, the taller of the two, was 180 cm (5 feet 11 inches), and both of them were fairly sedentary, this represents a significant amount of calories without any weight gain. During the first weeks, weight loss was more significant, apparently due to a shift in the water content of the body. Both men appeared "ruddier" at the end of the experiment than at the beginning.
Blood pressure did not increase in either subject. Stefansson's blood pressure remained at 105/70 mm. throughout the study, while that of the other subject decreased from 140/80 to 120/80 mm. Salt intakes were fairly low.
No physical fatique or problems sticking to the diet were experienced by the two men. Only when the protein content of the diet increased substantially (45% of calories, 55% fat) did problems with digestion occur. Replacing excess protein with fat (20% protein, 80% fat) quickly resolved them, however.
No clinical evidence of vitamin or calcium deficiency was noted, despite the diet being both acidic and low in calcium. In addition, the mild gingivitis Stefansson had suffered from, cleared up entirely during the meat diet. Interestingly, Andersen reported that his hair stopped falling out shortly after the meat diet was started; Stefansson also noted his hair started growing thicker and his scalp was healthier.
Acetone bodies in daily averages per experimental period ranged from 0.4 to 7.2 gm, with the maximum excretion measured during the year being 12.3 gm. The acidity of the urine showed a 2-to 3-fold increase, which is consistent with the highly acidic nature of the diet. A slight increase in uric acid nitrogen was found during the first three months only.
All in all, no evidence of irritation to the kidneys was found - despite the fact that these men were in ketosis practically for an entire year. A higher degree of ketosis was noted when the fat content of the diet increased and the protein content decreased. Acetone bodies quickly disappeared when carbohydrates were introduced into the diet.
In general, the men were in ketosis whenever the ratio of fat to carbohydrates was over 1.5. With the extremely small amounts of carb in their diets, no definite relation between the amount of acetone bodies and the ratio of fat to carbs was found. Stefansson's friend, who was smaller and had less subcutaneous fat, had the highest sustained ketosis.
Seven years after the meat diet
In 1935, one of the authors published an article titled "A Year's Exclusive Meat Diet and Seven Years Later", in which he revisits Stefansson's case (link). First, he summarizes the main points of his earlier article from 1926, titled "The Effects of an Exclusive Long-continued Meat Diet". The following medical facts regarding Stefansson's life during his explorations are listed:
- He spent altogether altogether eleven and one-half years within the Arctic Circle.
- He lived for a number of days, totaling nine years, on an exclusive meat diet.
- He lived for nine successive months on an exclusive meat diet.
- He reached his maximum weight while subsisting on meat (fish).
- His sense of physical and mental well being was at its best during that period of his life.
- He found that the exclusive meat diet worked as well when he was inactive as when active, and as well in hot weather as in cold.
- Constipation was never present. One month's entire absence from exercise produced neither constipation nor muscular weakness. (Stefansson avers that not a single case of constipation was observed in 600 exclusively meat-eating Eskimos for a period of three years).
- His hair thickened, and his scalp became healthier.
- Tooth decay was apparently much less rapid.
During this period, Stefansson had put on quite a bit of weight. He now weighed 84 kg, compared with 70.8 kg in 1922 and 72.5 in 1928. His hair was as thick as before, but his gingivitis had returned. Blood pressure was up to 120/80 mm. All in all, the author states Stefansson was in excellent general health. Looking at the numbers, however, it seems that he was doing better on his monotonous carnivore diet.
While it would be interesting to replicate the study with a larger sample size and have more health markers measured than the ones used in the study, it is quite remarkable to see that a diet consisting of nothing but meat and animal fat is both feasible and, apparently, healthy. It also lends support to the importance of having a sufficient amount of fat in the diet, especially when protein is present in significant quantities.