Starting LCHF can be scary. The low-carb bit is easy enough: you just stop eating carbs. The high-fat bit is harder, because you have to get past a lifetime of programming telling you that dietary fat causes your arteries to instantly harden and fur up, and your heart to explode.
Presumably, if you’ve got to this point, you’ve at least reached an intellectual understanding that this is wrong. Once you’ve completed the induction phase, you’ll have an emotional and physical understanding of the ‘rightness’ of dietary fats, and it’s all downhill from there.
What is induction, and why do we do it? The concept can be fairly ascribed to Dr Atkins, who (as far as I know) was the first to describe the scientific basis for it. It turns out that human bodies need a bit of a kick to make them switch on their alternative (fat-based) power source; if you try to reduce carbs slowly, the most likely outcome is that your body will protest, and that’s not what you want. However, if you give it no viable option for a few days, it’ll reconfigure everything to run on fat instead of glucose, and it’ll keep that configuration even when you (cautiously) reintroduce a few carbs.
The ‘kick’ takes the form of a drastic carbohydrate reduction and an equally-drastic increase in dietary fat. This isn’t as awful as it sounds. The reason is that carbs are often packaged with other things (water and fibre, mostly) whereas fats are not. Cooked rice, for example, contains about 1kCal/gram (not 4kCal/gram, which is the figure for dry starch). Butter and coconut oil, by contrast, contain 7kCal/gram and 8kCal/gram, respectively. In other words, a little fat goes a long way: you’ll need 150g+/day initially, and it’s surprisingly easy to incorporate 50g+ of fat into each meal. An 8-ounce steak, for example, includes 40g of fat even if you trim off the obvious lumpy bits. Cream is 25+% fat, so 40g in your coffee is another 10g.
During induction, your carbohydrate target is 25g/day ... or less. This is hard. It means eliminating all of the following:
-Sugar.
-All forms of grains, flour, starch. That means no cereal, pasta, bread, rice, or even cornflour thickener.
-Any plant foods with a high starch or sugar content. That means potatoes, carrots, tomatoes, and basically all fruit.
-Margarine. Yes, it’s a fat. The problem is that it’s a synthetic one, and your body will do odd things with it. Don’t eat it.
-Fizzy drinks. Or in fact any drink with sugar in it.
-Beer and wine. Don’t worry, you’ll be able to bring these back soon!
Unfortunately, induction is best described in terms of the limited range of foods you are allowed to eat, rather than the foods you can't eat:
-Salad and green veg. It’s important to have plenty of these on your plate, and there are lots and lots of choices. Be adventurous. LCHF is absolutely NOT about meat. Do your research online if you’re not sure if a particular vegetable has a high carb content – not many do.
-All meat, fish, and seafood; avoid lean cuts.
-Eggs.
-Fat-based spreads/condiments/dressings: butter, lard, olive oil, coconut oil, mayonnaise, cream.
-Beans, but only in very small amounts. Preferably green beans rather than the dried sort.
-Nuts, again in modest amounts.
-All forms of dairy products except milk (go easy on yoghurt and soft cheeses)
A lot of people find it hard to go cold turkey on sugar. It’s perfectly OK to use sweeteners for a while, but try to reduce them such that you’re down to zero after a month or so.
A vitamin pill can’t hurt, but it’s not essential.
It is critically important that you do not stint on fat. Try to get used to eating the fat on your bacon (a Full English, minus the toast and baked beans, is an ideal breakfast). Cook everything in a generous amount of butter or lard. Do NOT attempt to do a ‘low salt’ diet – on LCHF your body has a much higher requirement for salt, so feel free to add salt to taste. No need to overdo it, of course. Many people find a daily dose of meat-based soup helps maintain electrolyte balance, which can be somewhat disturbed during the first 3-4 days.
There is no calorie target, nor do you need a certain amount of protein. Just eat until you feel full. If you feel hungry, eat more. Eggs, or a piece of cheese, or a few nuts, make an ideal snack. Stay hydrated, but don't overdo it. Coffee and tea are fine, as long as they're sugar-free.
Desserts are, unfortunately, verboten. If you really want something dessert-like, go with Greek yoghurt or sugar-free jelly (add some cream).
Don’t be unduly perturbed if you feel a little rough during the first week. It’s quite normal to feel slightly light-headed or weak while your body adapts: I would compare it to something like a mild hangover (three pints the night before) or the feeling of malaise you get before the onset of a cold. It’s not “lack of carbs” as such, it’s just that your metabolism needs time to figure out that there are no more carbs coming. You will wake up one day feeling just fine.
How long do you need to keep this up for? Well, as long as you can cope with it. No less than 10 days, preferably 14. During this ultra-low-carb phase, you will see rapid weight loss. You’ll lose about 1kg over the first week, although sadly this is mostly water. You’ll probably lose 1kg of actual fat over the next week.
Two weeks in, most people have had enough and want a bit more variety. Fortunately, the most noticeable effect of induction is that you have a much-reduced desire to eat carbs. It’s OK to bring back moderately-starchy vegetables like pumpkin, carrots, and sweetcorn, plus milk and fruit … in small amounts. I do not recommend going further than that.
Around this time you will also notice a reduced desire to eat fat. This is because your body is now sourcing a lot of its energy from your own bodyfat. Just listen to your appetite and dial back a little on the dietary fat.
By the end of the first month, you’ll be completely fat-adapted and will probably be able to walk past a doughnut shop with only a slight twinge of regret. Six months later, you won’t even notice doughnut shops.
A few things to be aware of:
Whatever you’ve read on the internets, you will not die if you stop eating carbs. If that were true, I’d have been dead long ago. As noted, you’ll feel a little odd somewhere between day 3 and day 6 of induction (it varies). This will get better, not worse. If you DO feel really, disastrously ill, then you may have some undiagnosed medical condition and you should revert to your previous diet and consult your doctor; however, this is incredibly unlikely. LCHF induction is not in any way harmful for people with normal metabolism.
If you are diabetic, or if you are taking any kind of medicine, talk to your doctor before doing this. Many of the drugs which are fashionable today are designed specifically to slap a band-aid on the problems caused by high-carb low-fat diets. In many cases, they do this by interfering with metabolic pathways which are critically important for LCHF: in other words, your doctor will need to get you off those drugs before you can attempt LCHF, or it will not work properly. At worst, you could find yourself in serious trouble because the drugs are preventing your body from dealing normally with the new diet.
There are two common mistakes that people make with LCHF induction: a) trying to ‘improve’ it by reducing the fat or the salt, or b) not fully understanding how much fat is required because they are so used to skimping on cooking oils, buying lean cuts of meat, or discarding fat trimmings. It is almost impossible to eat too much fat during LCHF, but it’s certainly possible to eat too little.
Finally, I would advise you not to make too much song and dance about your diet; you will meet a lot of hostility and well-meaning (although annoying) advice about how terribly dangerous it is to eat fat. Nod and smile, and stick to the plan.
How many carbs a day are considered low carb?
Hi I’m back low carbing 
Extreme lethargy/fatigue on low carb?
Bowel movements low carb eating