Well, it's that time of year when we'll all be making New Year resolutions (and then promptly forgetting about them ). There's been an upsurge in posts concerning low-carb (LCHF) recently, so if you're thinking of giving this a go after your holiday indulgences, herewith a short FAQ ... and a bit of mythbusting.
There is so much misinformation written about LCHF that many people who believe that they're "doing low-carb" or "going keto" are actually not. There are many ways to get low-carb wrong (the first few weeks are particularly critical). However, if you get it right, everything just drops into place.
What is LCHF?
It stands for "low carb high fat", but it's a bit of a misnomer. You'll certainly be reducing your carbs close to zero in the first two weeks, and adding quite a lot of fat, but after a few months the macronutrient profile will change, and your meals will not look radically different to anyone else's. You'll be eating a varied diet with lots of vegetables, nuts, some fruit, and a modest amount of animal protein if that's your thing. All the things that the experts say are good for us.
What is a "keto" diet?
Your body has many different possible fuel sources - some are derived from your diet and some are synthesized internally. They're all in use at any given moment, but your dietary habits will alter the ratio in which they are used. A "keto" diet is one which is very low in carbs, forcing your body to use mostly fat for fuel, which it burns in the form of acetoacetate or beta-hydroxybutyrate (ketones), fatty acids, or glucose,after performing various conversions. Unlike LCHF, a keto diet demands strict adherence to a low carbohydrate intake at all times.
My nutritionist says that all bodies need glucose, and if I don't eat carbs I'll die.
The nutritionist is wrong (most nutritionists are, most of the time). It's true that human bodies need some glucose, but carbs (starches) are not the only source. A fat molecule (a triglyceride) is built on a glycerol backbone, which your body can convert via a simple chain of reactions into glucose. Every fat molecule that's released from bodyfat storage undergoes this process; that is, every fat molecule delivers three fatty acids, and half a glucose molecule. Most of your body's organs can burn the fatty acids directly, or after conversion to ketones. Excess amino acids (typically liberated from cell reconstruction processes) are also converted to either ketones or glucose.
The only hard requirement for glucose comes from your brain, blood cells, and corneas, amounting to few hundred kCal per day.
So a low-carb diet causes fat-burning?
It's a bit more complicated than that. It's true that low-carb diets cause your body to rely heavily on fat for energy, but that isn't the primary reason why your bodyfat reserves become depleted. It's more accurate to say that, when you're eating adequate fat and minimal carbs, your body has no need to maintain a large mass of bodyfat. One of the functions of bodyfat is to buffer the large, uncontrolled power surge from a meal heavy in refined starches, so when you stop eating such things, your body has no need for all that bodyfat, and it will start to discard it.
I don't want to eat more fat. Fat causes heart disease.
It's depressing that this myth refuses to die. It just stumbles on like an ideological zombie, refusing to accept that its head has been cut off, and propelled along by nothing but voodoo. Nobody has yet pinned down what causes heart disease, but one thing now seems fairly clear: it's nothing to do with fat, saturated fat, or cholesterol. Interestingly, what put the final nail in the coffin was a series of scientific trials on drugs which either reduce total cholesterol (statins),reduced LDL (statins and PCSK9 inhibitors), or increase HDL (statins and niacin). All of them do exactly what they say on the tin. Unfortunately, what they don't do is have any effect on either heart disease or total mortality - in fact several of them caused additional deaths in the intervention arm of the trial. Ooops.
On the other side of the coin, millions of people are now eating LCHF diets, and steadfastly refusing to develop heart disease - in fact they're generally much healthier than people eating the Standard Western Diet, as well as being slimmer. The nutritionists call this a "paradox". Scientists call it "disproof".
What's the difference between LCHF and Atkins?
Not a lot. The main ones are:
a) Atkins went a bit overboard on his carb restrictions. His prescription for induction was basically spot-on, but he was incorrect about the general ability of humans to tolerate carbs. The vast majority of people can eat quite a lot of carbs - at least if not eaten at every meal - without gaining weight.
b) He suggested eating protein "ad lib", and many people thought this meant "eat as much meat as possible". All he actually meant was that you don't need to measure it. LCHF discourages excessive protein, for various boring reasons.
How do I do this right?
You'll proceed in two distinct phases - induction and weightloss. "Maintenance" is considered a third phase, but it's really a continuation of the second; you don't have to think about switching from "weightloss" to "maintenance" because it just happens all by itself.
In the first stage you'll go keto. You eliminate all visible carbs from your diet and add fat to your meals in quite large amounts; any source is acceptable, but highly-processed vegetable oils are best avoided (canola, corn, etc). Most people find the best way to do this is to add lots of vegetables with fat-based sauces or dressings; for example, by roasting vegetables in olive oil and butter. You can also add dairy fats ad lib to (for example) scrambled eggs, or coffee. Milk should be avoided at this point, but cream and Greek yoghurt are fine. All low-fat food substitutes should be avoided!
There is no need to add extra protein. You might find you're eating a little extra meat as you consume extra meat fat, but it's unlikely to be very noticable.
After a while you'll simply get sick of adding fat to your meals. This typically coincides with the onset of fat loss - you'll probably see it happening in your face any belly before it registers on the scales. Your appetite will drop and you will naturally dial back on the butter, cream, etc. Congratulations, you're now in the weightloss phase. This will continue for several months, during which time you'll feel inclined to add back the occasional dose of carbs (such as fruit or a slice of wholemeal bread), and there's nothing at all wrong with that.
How do I do it wrong?
There are unfortunately several ways to mess this up:
- Trying to substitute more protein instead of fat.
- Not eating enough vegetables (if you do this your meals will be unpleasantly greasy, and you may not get adequate micronutrients).
- Not recognising where the carbs are lurking; root vegetables and fruit are common culprits, as are things-in-packets that purport to be "low sugar" but are still very high in starches.
- Trying to do low-salt while on low-carb. Contrary to popular opinion, most people are eating too little salt. If you experience muscle cramps or weakness, you may have inadequate salt intake.
- Trying to count calories. You eat when you're hungry, and stop when you're full. Under no circumstances should you attempt to control your portions. Let your appetite tell you when enough is enough. It may get things a bit wrong for the first day or two, but it'll rapidly sort itself out.
For those who are interested, there's a group for LCHF:
But as you may have noticed, many of the members here are doing some variant of low-carb. Because it works.