“For every expert, there is an equal and opposite expert”.
-Clarke’s Fourth Law
The low-carb high-fat diet has been around for at least 100 years, and it does what it says on the tin: it helps you maintain a healthy weight, it reduces your risk of heart disease and diabetes, and it can often fix niggling problems like bad skin. It is also, according to popular opinion, the world’s worst “fad diet”.
I’ll briefly define what LCHF actually is, because most expert commentators don’t know. An LCHF diet – surprisingly enough – is low in carbohydrates (starches) and high in fats. Protein can be anywhere in the normal range, from about 0.6g/kg to 2g/kg, depending on how active you are. Practically speaking, a typical LCHF meal involves lots of vegetables, a modest amount of meat and/or dairy, and often some kind of oil or fat for cooking – olive oil, coconut oil, lard, and butter are popular. Although it’s not mandatory, most adherents advocate minimally-processed food, and a wider range of ingredients. LCHF is not a diet as such but a philosophy for eating – there are many diet plans based upon it, with Atkins being probably the best known (and the most ridiculed).
This stands in contrast to what I will describe as the Establishment Diet, which in its idealised form is based on starchy foods such bread, rice and pasta, with some lean white meat. Fats, if eaten at all, should be unsaturated vegetable oils. While the Establishment do exhort us to consume ‘five [fruits and vegetables] a day’, this is presumably a lesser quantity than the recommended six to eight daily servings of carbohydrates (depending on who you ask).
So let’s be absolutely clear: a contingent of vocal experts is telling us that it’s terribly unhealthy to eat the meat, vegetables, and dairy products that sustained our forebears for millennia. Instead, we should eat foods that were either economically or technologically impossible to produce in large quantities until the Industrial Revolution. Western populations have followed the expert advice to the letter, and despite living longer lives (mainly due to vaccinations and better hygiene), quality of life has plummeted. People are fat, ill, and depressed. Many are taking cocktails of drugs of dubious value. Diabetes is rampant and uncontrolled, with many sufferers losing their eyesight or limbs in middle age.
How we placed ourselves in this predicament is worth exploring, and I’ll do so later, but in this first post I’d like to provide a quick-start manual for LCHF, for the benefit of new members or those who are curious about the concept.
Some condensed science first. Your body’s main “fuel” is acetyl coenzyme A (acetyl-CoA), which is a sort of articulated truck for delivering energy from food and from storage into the Krebs cycle – the hair-raisingly complex sequence of intracellular chemical reactions that ultimately pumps out ATP, the recyclable molecule that drives your body’s machinery. A whole bunch of conversion pathways exist to create Acetyl-CoA from various things, including fats, starches and sugars from your food, fatty acids from your fat cells, glucose from stored glycogen (in your liver and muscles), or from ‘ketone bodies’. Ketone bodies are perhaps best described as an alternative form of acetyl-CoA, produced by the liver; acetyl-CoA is readily converted either to or from ketone bodies, which are essentially twinned-up acetyl groups with coenzyme-A detached.
Contrary to popular opinion, your body does not care where acetyl-CoA comes from: it certainly doesn’t have to come from glucose. Most bits of your body have all the metabolic machinery to derive acetyl-CoA from any of the possible inputs, although a small number of exceptions have more limited options – notably, your nervous system, your red blood cells, and your retinas. Your liver can synthesize glucose (from lactate, alanine, glutamine, or the glycerol backbone of fats) for those few cells that need it, if it’s not directly available from ingested starches and sugars. However it is surprisingly hard to reduce dietary carbohydrates low enough that this process becomes critically important.
The TL;DR version is that your body is equally happy using either fat or glucose for energy (and to a lesser extent, proteins). While many sources insist that weakness and ‘brain fog’ are inevitable on a fat-based diet, there is no biological reason why this should be so, and neither does it happen in practice. Researchers have found no difference between athletic performance in ‘fat mode’ or ‘glucose mode’, as long as the athlete is given enough time to adapt to a fat-based diet.
But why would anyone WANT to use this fat pathway? Doesn’t dietary fat give you heart disease?
Well, no, it doesn’t. Even on a high-carb diet, the link between fats (or specifically saturated fats) has never been particularly strong. Huge, expensive research projects have failed to find a definitive cause-and-effect. What we do know, however, is that a carb-based diet of the Establishment type will make you fat. By the time most Westerners hit middle age, they’re distinctly baggy at the seams. This is not normal, and it makes a lot of people miserable. The simple explanation is as follows: fat storage is mediated by insulin. Insulin rises when carbohydrates are ingested and delivered into the bloodstream as glucose; this is a signal to all cells capable of using glucose to remove glucose (and other things) from the blood, thus maintaining blood sugar within the required range. More often than not, that glucose ends up being stored as fat: it's entering your body faster than you can use it. Eat carbs at every meal and your body is always storing, never burning. A low level of insulin, conversely, is a signal for the liver to release glucose into the blood, and for fat cells to release fatty acids.
A carb-heavy diet appears to trigger diabetes in an unlucky few, and there is increasing evidence that the saturated-fat issue has been a case of mistaken identity. It’s true that people who go on to develop heart disease have high levels of circulating saturated fatty acids. It turns out, however, that those fatty acids are the output of the body’s own fatty-acid synthesis pathway: they were originally excess carbohydrates, and they have noplace to go. Whether this is a causative mechanism behind atherosclerosis is still unknown, but at best, it appears to be a symptom that a body is in metabolic distress.
So how do we do this?
The adaptation phase is probably the most widely-misunderstood aspect of LCHF. Sometimes called ‘keto’ (short for ketosis), it involves a two-week period of extreme carbohydrate restriction. 25g net carbs is typical. Your body is essentially forced to burn only fat for energy – because nothing else is available. When carbohydrates are cautiously reintroduced, it carries on using that fat-burning pathway.
To achieve adaptation, you’ll go cold turkey on sugar, bread, pasta, potatoes, and ALL other sources of starch. You’ll eat a lot of salads and vegetables. You’ll add fats and oils – that typically means cooking with butter, making dressings with oils, and using fatty cuts of meat. You’ll be using cream instead of milk. You certainly won’t be eating dessert, although jelly (without sugar) is fine.
Most people feel slightly uncomfortable during this period. Ketones are excreted in the urine until your body starts to figure out what to do with them (people often use ketone test strips to check this, which indicates things are going according to plan). Although the term ‘keto flu’ is used, it’s nothing like flu: at worst, it’s that mild feeling of malaise that you get when you’re coming down with a cold, and it passes in about 3 days.
Detractors will assert that this is outrageously dangerous, "because ketone bodies acidify the blood". This is nonsense. Your blood pH is buffered, and ketone concentrations are regulated. Unless the buffering action is overwhelmed by an enormous quantity of ketones – something that can happen to diabetics and alcoholics – there is nothing unsafe about ketosis.
The naysayers will also assert that attaining ketosis demands such a boring diet (this is true) that nobody can stick to it for any length of time (also true). However, unless you want to, there is no need to do so for more than a couple of weeks. After that, you’re into a weight-loss phase.
Atkins, in his book, describes an overly-cautious approach to the weight-loss phase. Subsequent research suggests that, once induction has been achieved, most people can eat almost anything as long as they avoid sugar, potatoes, and flour-based products, and they will continue to lose weight. Carrots, fruit, and even things like icecream and chocolate, are OK in moderation.
Once you’ve achieved your desired weight – which will likely happen very rapidly – you’re into the maintenance phase, and here’s where the real magic happens. You’ll find that you no longer WANT to eat things that make you fat. Your appetite is working again. Far from being “impossible to adhere to”, LCHF feels the most natural thing in the world.
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LCHF plan