Liquid Protein diets and Sudden Death
A concern is the sudden deaths associated with the liquid protein shake VLCD diets in the 70s and 80s. Now yes, there was a major issue with the type of protein used but it wasn't the only issue. Of course there have been improvements in the quality and thus safety of these liquid meal replacement diets over the short term (though they still carry lots of risks). However, they do not show any safety for unsupervised diets - let alone ones that are simply a stab in the dark and offer no real nutritional guidelines and minimums, to avoid risks associated with VLCD dieting and fasting.
I should add to this, that a little while back in the space of a little over a week, I had heard of two incidents by people whom had allegedly run into heart trouble whilst following a particular VLCD that was popular amongst low carb circles in the US a few years ago. The last person apparently had dangerously low levels of potassium, that is not something to be messed with. The fitday in which allegedly belonged to this person appeared to have fat under 30g but mostly under 20g. Protein choices were mostly protein shakes, chicken, egg, fish and turkey and went back to early June so this person would appear to have been on this diet for over 2 months when they ended up in hospital. I haven't heard any more of these two incidences since.
"IN 1976 a book entitled The Last Chance Diet was published and almost immediately, several liquid-protein-modified-fast (LPMF) diets became very popular and fashionable as means of rapid weight reduction. These diets were intended to serve as the dieter's only source of calories. Between January 1, 1977 and December 31, 1977, it was estimated that more than 100,000 persons had used one or more of the LPMF diets as their sole source of nourishment for at least 1 month. By August 1977, however, sudden death in several young LPMF diet users was reported to either the Food and Drug Administration (FDA) or the Center for Disease Control (CDC), and between July 1977 and January 1978 at least 60 deaths among avid users of the LPMF diet were reported to the FDA and CDC. " 
One study discussing the dieters that died from sudden death in the late 70's and cardiac dysfunction, speculated that[I] "Although little is known about the pathogenesis of the acquired QT syndrome exhibited by certain persons during and for a variable periods of time after prolonged caloric restriction, it is likely that severely obese individuals who have lost 30% or more of their body weight rapidly, either by fasting or by means of VLC diet, are at substantial risk of developing this dangerous cardiac disorder. Less obese persons who reduce their weight rapidly on similar regimens may develop a prolonged QTc interval after losing as little as 10 to 15% of body weight, In such individuals, death from ventricular arrhythmia could occur within 2 months of dieting."
This is why I have a problem with people following very low calorie diets written by your average anonymous person on an internet forum. Who is to say, that a future dieter or two (or three) does not have the potential for sudden death through following their diet plans and advice? How do we know that their plan, is any better then the old liquid protein diets of the past that were associated with sudden deaths?
But there's more, there is also concern regarding diets consisting of mostly lean protein, a concern that was commonly shared by arctic explorers.
The term "Rabbit Starvation" is well known amongst explorers. I have seen this term mentioned in a lot of discussions regarding lean protein and low carb including low carb research papers. If you have been keeping up with this whole kimkins controversy then you have probably seen the term mentioned many times amongst kimkins related discussions as well. The one they usually refer to is, Vilhjalmur Stefansson whom spent many years with the Eskimos, which included eating their diet. I found some of his writings which I will share:
Quoted by Vilhjalmur Stefansson in his book The Fat of the Land, page 30:
"The groups that depend on the blubber animals are the most fortunate in the hunting way of life, for they never suffer from fat-hunger. This trouble is worst, so far as North America is concerned, among those forest Indians who depend at times on rabbits, the leanest animal in the North, and who develop the extreme fat-hunger known as rabbit-starvation. Rabbit eaters, if they have no fat from another source-beaver, moose, fish-will develop diarrhea in about a week, with headache, lassitude, a vague discomfort. If there are enough rabbits, the people eat till their stomachs are distended; but no matter how much they eat they feel unsatisfied."
He and other explorers termed this diet 'Rabbit Starvation' or 'Rabbit Malaise'.
I was reading his book titled, My life With The Eskimo on google book search and I found this on page 27 and 28:
"In certain places and in certain years rabbits are an important article of diet, but even when there is an abundance of this animal, the Indians consider themselves starving if they get nothing else, ~~ and fairly enough, as my own party can testify, for any one who is compelled in winter to live for a period of several weeks on lean meat will actually starve, in this sense : that there are lacking in his diet certain elements, notably fat, and it makes no difference how much he eats, he will be hungry at the end of each meal and eventually he will lose strength or becomes actually ill."
Then page 140:
"Of our entire seven I was now the only one not actually sick, and I felt by no means well. Doing hard work in cold weather on a diet nearly devoid of fat is a most interesting and uncommon experiment in dietetics, and may therefore be worth describing in some detail. The symptoms that result from a diet of lean meat are practically those of starvation. The caribou on which we had to live had marrow in their bones that was as blood, and in most of them no fat was discernible even behind the eyes or in the tongue. When we had been on a diet of oil straight, a few weeks before, we had found that with a teacupful of oil a day there were no symptoms of hunger; we grew each day sleepier and more slovenly, and no doubt lost strength gradually, but at the end of our meals of long haired caribou skin and oil we felt satisfied and at ease. Now with a diet of lean meat everything was different. We had an abundance of it as yet and we would boil up huge quantities and stuff ourselves with it. We ate so much that out stomachs were actually distended much beyond their usual size ~~ so much that it was distinctly noticeable even outside of one's clothes. But with all this gorging we felt constantly hungry. Simultaneously we felt like unto bursting and also as if we had not had enough to eat. One by one the six Eskimos of the party were taken with diarrhea.
By the 10th of January things were getting to look serious indeed. It was apparent not only that we could not go on indefinitely without fat, but it was also clear that even our lean meat would only last a few days longer. We had on December 11th estimated that we had two months' supplies of meat, and now in a month they were gone. Our estimate had not been really wrong, for if we had had a little fat to go with the meat, it would no doubt have lasted at least sixty days, but without the fat we ate such incredible quantities that it threw all our reckoning out of gear. "
I can't access the next page so I have no idea how much more he goes into it, if anyone does please share :)
I found another book by Stefansson on google books titled, Unsolved Mysteries of the Arctic, here's an excerpt from page 248-249 which whilst discussing rabbit starvation also discussed something that is so relevant today, lets see if you can pick it:
"It is widely accepted, and probably correct, that the chief difficulty in shifting from a mixed to a meat diet is psychological~~a digestive revulsion based upon the idea that meat is dangerous. For, until recently, it has been a common belief that you cannot be healthy unless you have a varied diet, that meat is injurious if taken in large quantities, and that you become "tired of a monotonous diet". The Andree party do not seem to have had any such inhibitions. This may have been because they were familiar with the history of human diet and knew that nations and races have lived for centuries and millenniums on a diet mainly or exclusively meat. More likely they expected the desirability and palatability of a meat diet through the recent experience of Nansen and Johansen who, as we have noticed more then once, spent a whole winter (a little farther north than the Andree party would be spending theirs) on an exclusive meat diet, coming out in the spring with the best of health."
"It is a nearly universal experience, when a shift is being made from a mixed to a meat diet under such conditions as those of the Andree party, that there is little or no prejudice against the lean of the Arctic animals but considerable against the fat. This fat is called blubber, is supposed to be a reprehensible, and the very thought of it commonly nauseates the inexperienced."
"But it has been found in various parts of the world that a diet of lean meat exclusively will cause diarrhea in from three days to a week. If no fat can be added to the lean, the diarrhea becomes serious and will lead to death. A well known field where such deaths occur is the northern edge of the forest in Canada where Indians are sometimes unable to find any food except rabbits. The expression "rabbit starvation," frequently heard among the Athapsc [/I][I]Indians north-west of Great Bear Lake, means not that people are starving because there are no rabbits but that they are going through the experience of starvation with plenty of rabbit meat. For this animal is so lean that illness and death result from being confined to its flesh."
"When a party like Andree's are making a gradual shift from a mixed to a meat diet, no diarrhea will appear in the early stages; for there is still a considerable percentage of sugars, starches and the accustomed fats such as butter and bacon. When these elements are materially lowered, and meat begins to play a larger and larger part, you approach the diarrhea stage. The trouble, once begun, will continue until the party overcomes its prejudice against"blubber" and begins to use fat enough to make up for the things (like potatoes, bread and sugar) which are normally eaten by a man fond of beefsteak who, when he eats steak, trims the fat away."
They also did a study a few years later where both Stefansson and Anderson lived for one year on an exclusive meat diet . Also if you are interested in reading more there is an old article by Stefansson available called Adventures in Diet that I have made available to others to read.
I find these excerpts above very interesting... Here's a quote from a study on hunter gatherer diets: 
"Many historical and ethnographic accounts have documented the deleterious health effects that have occurred when humans were forced to rely solely on the fat-depleted lean meat of wild animals. Excess consumption of dietary protein from the lean meats of wild animals leads to a condition referred to by early American explorers as "rabbit starvation," which initially results in nausea, then diarrhea, and then death. Clinical documentation of this syndrome is virtually nonexistent, except for a single case study."
"Muscle tissue of wild ungulates typically contains 2.0-3.0% fat by weight. Lean muscle meat of ungulates (2.5% fat by wt) is composed of 79.8% of energy as protein and 20.2% as fat. Consequently, consumption of lean ungulate meat as the sole daily energy intake would rapidly exceed the ability of the liver to eliminate nitrogen as urea and, hence, produce symptoms of rabbit starvation."
According to the nutrition data web site, stewed chicken breast without the skin and bone contains only 18% fat as energy whilst, roasted turkey breast meat 5% fat, light canned tuna in water (drained) 6% fat, egg whites are a mere 3% and protein shakes most likely even less. Keep in mind that the lean meat they are referring to in the quote above is 20% fat. Then we have a quote by Loren Cordain:
"The human physiologic protein ceiling is, in short, the upper limit of dietary protein that humans can digest. Small animals have less fat and more protein for their size than large animals do. The total protein content of a rabbit may be as high as 75%, with 25% fat, while a large animal may be only 35% protein and 65% fat. The maximum amount of protein humans can process at one time is about 35% to 40%. Therefore, using rabbits as a food source will rapidly exceed our protein ceiling, causing a syndrome referred to by early arctic explorers and frontiersmen as "rabbit starvation." Despite eating huge amounts of lean meat, men afflicted with rabbit starvation quickly became lethargic and developed diarrhea; death eventually followed."
So if you think this couldn't possibly happen to you or someone close, think again...
I know of quite a few that have tried anonymous very low calorie diets on internet forums, where they eat lean meat and egg only and after a few days they go nuts and start binging through no fault of their own. I wonder, if there was nothing else available-so that all they could binge on was the lean meat, if they would then get diarrhea and so on as described by Stefansson?
Of course, granted there were some doing this that have the opposite problem, so I am not sure what that means. I have read of others having unexplainable diarrhea.
Muscle and Metabolism
Stefansson speaks of this unsatisfying hunger, I feel it certainly fits with the thought that excess protein converts to glucose, doesn't it?  it would also explain some of the incidences where people go right off the rails despite doing every thing right... of course I do think this protein theory as in how much you convert to glucose and how often and how it effects you is individual, but I have seen it myself where some people seem to do this very easily.
The worst bit about the possibly in that environment, is that if your protein is being converted into glucose so much as to invoke such hunger, then would that also keep your glucose metabolism dominant and thus more likely to burn muscle when calories are low?
Burning muscle is something you really want to minimise when trying to lose weight. Other then the more obvious benefits of having muscles, it also uses up more energy then fat just to maintain thus the higher your muscle mass the higher your energy needs. The more muscle we lose the more we lower our energy output which for obvious reasons impedes weight loss. Granted, some muscle is going to be lost during weight loss anyway, but if we lose too much particularly in comparison to our fat loss, we pretty much shoot ourselves in the foot.
There is a good article I found a while back that explains it really well 
Being a fertile woman I found this paragraph towards the end of the article scary:
PHYSIOLOGICAL PHENOMENA OPPOSING WEIGHT REDUCTION
"As we saw, if the energy intake is permanently reduced, body weight also reduces until it produces en energy expenditure equal to the intake, and the size of the reduction is inversely proportional to the consumption of the weight loss, which in turn depends on its composition that is determined by the starting weight. As already mentioned, a drastic diet, either in absolute terms (less than 1,200 Cal/day) or in relative (more than 500 Calories less than the starting TEE), causes the loss of a weight containing a percentage of lean body mass greater than what would be physiological for that definite starting weight. This phenomenon, which was proved in fertile women, while the clinical experience and the results of our studies suggest that it does not occur in postmenopausal women or in men, has two types of negative consequences. On one side, starting from the same body weight, since the weight loss consumes more, for a definite cumulative reduction of energy intake less weight is lost, even if in shorter time, than what would be if the weight loss composition was the physiological one. On the other side, with the weight attained being the same, since more lean than due was lost, body weight contains less lean and more fat, and then it consumes less. This means that to maintain any weight after a drastic diet one has to eat less than another person who has lost the same weight with the physiological composition, or a person with equal body weight who never lost weight. But the worst aspect of this phenomenon is that the alteration of body composition that it causes is permanent. In fact, in the case of weight regain after a drastic diet, the composition of the weight regain is the one physiological for the starting weight. Thus, less lean and more fat are regained in comparison with what was lost, and consequently also the maintenance of a weight equal to that prior to the diet entails an energy intake smaller than that before dieting. And, since the alternative is to go back to the previous energy intake stabilizing at a higher weight than that before dieting, it is easily understood how a series of such ups and downs (which is defined as "weight cycling") may lead to a progressive weight gain progressively more difficult to control. Many young women with no genetic predisposition to obesity, misled by mass media and not protected by specialized surveillance, vainly pursue unrealistic beauty ideals and eventually condemn themselves to become obese or to stay on a diet all their life."
I will have to see if I can find anything that backs this up, but its not just about muscle mass, as there is also an impact on our thyroid which regulates our metabolism, amongst having an effect on other important things such as our cardiovascular system, central nervous system (e.g.: mental state), growth and development and our reproductive system .
An interesting study I found explores the effect of a high protein VLCD on resting metabolism, thyroid hormones and energy expenditure of obese middle-aged women. 
Whilst they found that RMR dropped due to muscle loss they also found that the extended dieting itself had an effect on T3 levels which did not return to normal within 5 weeks of refeeding. RMR dropped significantly during the diet and upon refeeding returned to near baseline but still lower then baseline.
They note that changes in thyroid metabolism may be a factor in decreased BMR which occurs as a result of prolonged severe caloric restriction. They mention that fasting or semi-starvation leads to decreases in serum T3, increases in rT3 and little change in T4. Whilst rT3 initially increased, they found by 10 weeks it had returned to baseline and kept on dropping until significantly below baseline which they feel may indicate an adaption to prolonged caloric restriction. During the 5 weeks of refeeding that followed the VLCD they found that rT3 and T4 did return to baseline but serum T3 whilst increased, it did not reach baseline levels. They state that declined serum T3 resulting from severe caloric restriction has been linked to diet induced decline in BMR. They mention a study by Moore et al that found that those whom had the slowest weight loss during a 320 cal liquid diet had the lowest RMR and serum T3 levels. They also mention supplementing T3 to counter this was not effective and if I am reading this right suggested that such supplementation promotes protein wasting in luei of fat loss. I should note for those interested that they mention a link between carbohydrate restriction and decreased plasma T3 levels during caloric restriction, click on the link above and scroll down to thyroid hormone changes. I thought I would mention that tidbit as some members on LCF (Low Carb Friends) have been recommending that those with thyroid problems shouldn't go below 30g to 40g per day.
Another study  found that RMR was still depressed 2 months after the completion of a PSMF (protein sparing modified fast) and that reductions in fat free mass again did not account for all of the reductions in RMR. Here's an interesting quote I found in this paper in regards to RMR changes in lean and obese individuals:
"Refeeding experiments with lean individuals suggested that the RMR decrement associated with severe caloric limitation reverses within days of resuming maintenance caloric consumption. However, the RMR of our obese subjects remained depressed after massive weight loss despite increased caloric consumption to a level that allowed body weight stabilization."
Leibel and Hirsch  found that during weight maintenance some reduced-obese or even partially reduced patients must restrict their food intake to approximately 25% less than that anticipated on the basis of metabolic body size.
This study  found a significant reduction in serum T3:
"Serum T3 decreased by as much as 66 percent in VLCD (Very Low Calorie Diet) patients during consumption of the 400 kcal/day diet, whereas rT3 increased by as much as 27 percent. T3 increased when patients were realimented with a 1000 kcal/day balanced diet but remained a significant 22 percent below baseline."
Plus another study on the metabolic adaption in women during a very low calorie diet found that after 21 days the decrease in RMR-LBM ratio was near to that of those suffering chronic under nutrition .
If anyone comes across any more research on this topic please feel free to share so I can add it to my VLCD Research page and possibly this page as well.