There seem to be a ton of folks on reddit - actually, the internet in general - who think that low carbohydrate/ketogenic diets are the secret to fat loss and health. Apparently, people just don't know enough about it yet.
So, I've taken it upon myself to summarize the "low carb" phenomenon as I've followed it very closely over the years. I'll spend more time addressing the modern manifestations of the diet (as that is more relevant to the online community) than its history.
William Banting made low carbohydrate dieting somewhat popular in the mid/late 1800s. It really wasn't until Irwin Stillman and Robert Atkins came along in the 1960s and 1970s that the diet really gained popularity. The early 2000s saw the Atkins Diet become extremely popular. This was really helped along with Gary Taube's 2002 article in the NY Times "What if It's All Been a Big Fat Lie?" Taubes went on to publish what most consider the bible of low carb research - Good Calories, Bad Calories. You'll rarely find anyone on a forum debating the merits of the diet without someone suggesting that detractors read this 640 page tome. He's recently published another book - Why We Get Fat and What to Do About It - to address concerns that the first book was too long and difficult for a layperson to understand.
Taubes says that "these competing ideas should be tested" and admits that such testing has not been done. Since obesity is such a serious problem, though, he says that we should institute his diet recommendations now without waiting for the evidence. That's the same thing he criticizes the low-fat diet campaign for doing. We went beyond the evidence and instituted society-wide changes based on inadequate data, with what Taubes considers to be disastrous results. How can he be so certain we should go beyond the evidence this time?
Many of the articles referenced in Atkins' book involved poorly-controlled studies. 9 of them weren't even published studies at all, but simple abstracts. Some were published in nearly unknown medical journals that aren't even indexed by the major medical databases. And most of the articles were published by Atkins-funded researchers.
The basis of the diet seems to be that insulin is terrible for your health and weight. The recommendation is to eat meat and fat and to limit carbohydrate consumption to keep insulin at bay. However, according to research published in the American Journal of Clinical Nutrition, meat and cheese actually cause more insulin secretion than even white pasta (http://is.gd/yShYfu).
It's interesting because the folks who were publishing books in the beginning all referenced each other. It gave a sense of credibility. You could turn to a page in Atkins and see several studies referenced and you might think there's a lot of good science behind the claims. You'd see the same in Protein Power by the Drs. Eades. The Weston A. Price Foundation was referenced frequently in various low carb books as well, even by Taubes. This organization seems to be less popular now than it used to be. Quackwatch is one of many skeptic websites that address their credibility: http://is.gd/Wq4X6F.
Initially, the concerns over the Atkins diet were the large amount of saturated fat that was believed to be bad for the heart. There was concern over the amount of protein which was thought to lead to potential bone loss and kidney problems. The loss of electrolytes and resulting problems with cardiac arrhythmia were concerning. The scientific consensus seemed to be that the diet just wasn't studied well-enough long term to be recommended. None of the major medical organizations endorsed its use (recently, the American Diabetes Association softened its position on the diet and suggested that it could be used for weight loss, but stressed the importance of monitoring blood lipids and kidney function).
High quality, longer-term studies that looked at ketogenic diets used for weight loss in particular began
in the early 2000s with the popularization of Atkins. Many found that weight loss was greater on the diet than others. Some found that diabetics had better glycemic control on Atkins (not surprising due to the low carbohydrate intake). Even others found favorable changes in blood lipids - HDL and triglycerides being the most improved. But LDL cholesterol was generally not affected by weight loss or actually increased on the diet. This is unusual for any weight loss diet.
The internet is full of people who think the "lipid hypothesis" is wrong. The International Network of Cholesterol Skeptics, for example. The topic is too complicated and drawn out to fully address here, but suffice it to say that the debate is tightly intertwined with the whole discussion of whether "low carb" diets can be healthy. Primarily, the debate is over whether LDL cholesterol. The discussion about LDL cholesterol being bad for you boils down to this: most healthcare practitioners see LDL cholesterol lowering as the primary goal for the reduction of risk of developing heart disease. There are two patterns of LDL. One is considered larger and less dense and the other is small and more dense. The recurring theme when addressing those concerned with increased LDL readings in the low carb community is to reassure folks that eating fewer carbohydrates almost assuredly changes your LDL to the larger, less dense type. Many have even gone on to say that this pattern in "protective" against heart disease, but compelling evidence doesn't seem to back this up and the primary goal is still to reduce total LDL cholesterol, regardless of the pattern. Even still, many in the low carb community think that the HDL:triglyceride ratio is more important.
The diet was said to have a "metabolic advantage." That was disproved. Then said to cause increased satiety, resulting in reduced calorie intake. Verified in the short term, but long-term, low carbohydrate diets don't do any better than any other diet - all diets have poor long-term adherence and most folks regain the weight they lose.
The diet hasn't been without other controversies. In the original Dr. Atkins' Diet Revolution, Atkins suggested that pregnant women could eat a low carbohydrate diet without issue. Later he issued the statement "I now understand that ketosis during pregnancy could result in fetal damage [...] I didn't study enough cases to validate my recommendation. If anyone wants a retraction, I'll be glad to give one."
In 2000, Dr. Atkins developed cardiomyopathy, stated to have been caused by a virus. His cardiologist went on to say that Atkins had a very healthy cardiovascular system. In 2003, he slipped on some ice and hit his head, ultimately leading to his death. Some folks obtained a copy of his death certificate via unethical means. They released it, showing that he weighed 258 pounds. The implication was that he was obese when he died, but the excess weight could have been from fluid retention during hospitalization. The Medical Examiner's report had a hand-written note that Atkins had a history of myocardial infarction (heart attack), congestive heart failure, and hypertension.
So, where does that leave the internet? During the days of Atkins, there were countless low carb forums, online stores. Blogs popped up all over the place. People started to make a living off of this diet.
One notable example is Jimmy Moore of "Livin' La Vida Low Carb." In 2004, he lost 180 lbs following the Atkins diet. He became one of the internet's most outspoken proponents of low carb dieting. He has been very open about the difficulties he has had maintaining his weight loss. Over the years, he's attempted many different variations on the low carb theme to stop his weight from creeping back up. One memorable example is his eggfest where he ate only eggs, butter, and cheese. Jimmy is a strong proponent of bringing together the low carb and paleo communities. Perhaps this is because paleo dieting has become much more popular and profitable.
In the past 5 years or so, really starting with Loren Cordain, the "Paleo" diet has become very popular. Cordain believes we should abstain from fatty meats and even goes as far as to suggest that folks douse their cooked lean meats in flax oil. The whole "low fat" (or, rather, "good" fat) Paleo diet isn't very popular with folks who lean toward a very low carbohydrate diet and/or love bacon.
We have folks like Mark Sisson, a man who makes a ton of money selling books, programs, retreats. He sells protein powder (Primal Fuel) that contains whey protein and casein. He suggests that folks consume nuts (including almonds) because they are "natural," but you should avoid beans because they contain phytates. In fact, nuts contain more phytates than beans. He seems to be very concerned about so-called "antinutrients" in "modern" foods like wheat, but tends to give things like spinach, which contains oxalate, a pass.
There is a lot of fragmentation in the paleo diet community. Some eschew most carbohydrates. Others suggest the use of "safe starches" such as sweet potatoes. So, it's pretty difficult to pin down what THE paleo diet is. Our ancestors ate diets that varied so widely that it would be impossible to point to a specific diet and claim that it is the one historical human diet. A good way to illustrate this is to compare the animal to plant ratio of calorie intake across hunter-gatherer peoples. The animal-derived calorie percentage ranges from 25% in the Gwi people of southern Africa, to 99% in Alaskan Nunamiut (http://is.gd/orjAW7).
So here we are on reddit. The /r/keto subreddit is very popular and there are many folks who post success stories, before/after photos. Just about every post that makes it to the front page about obesity, diet, or weight loss inevitably has a low-carb proponent mentioning how much weight they loss or suggesting that someone read about how what the medical community seems to accept as true about obesity and diet are all false and we should be eating lots of fat and few carbohydrates. These posts are often upvoted and unchallenged.
Science doesn't work the way a lot of folks in the low carb and paleo communities think it does. It's not about a bunch of folks who just blindly accept scientific dogma, who are easily disproved by anecdotal evidence. It's not about people just not accepting or understanding a couple of folks who have published their own books directly to the public. It's about doing the hard science. About looking at the preponderance of the evidence. Thus far, the quantity and quality of the studies and research done on the low carbohydrate diets popularized at the turn of the last century is still not good enough to recommend that the general population gorge on fat and protein.