Frequently asked questions

The ketogenic diet, or simply keto, is a way of eating with very few carbohydrates, usually under 20–50 grams of net carbs a day. You eat enough protein, and most of your calories come from fat. The aim is to get the body into ketosis.

In ketosis the body burns mainly fat. From it the liver makes ketones, which the brain and muscles use as fuel.

Keto does not suit everyone. If you have a medical condition or take medication, are pregnant or breastfeeding, have or have had an eating disorder, or are under 18, talk to your doctor first. What we write here is general information and does not replace a doctor’s advice.

Net carbs are the carbohydrates you count on keto. From the total you take away dietary fibre, which is not digested and does not raise blood glucose. Polyols, sweeteners such as erythritol, usually come off too, since most of them barely raise blood glucose (maltitol is the exception: it raises it noticeably).

How you do the sum depends on the label. On European Union labels, carbohydrates are already given without fibre, so you subtract only the polyols, if there are any. On US labels, “total” carbohydrates include fibre; there you subtract both the fibre and the polyols.

The usual mistake is to subtract the fibre a second time on a European product, which leaves you with fewer carbs than the food contains. And if the sum comes out negative, count it as zero.

Keto rests on foods low in carbohydrates: eggs, meat and fish, olive oil and butter, most cheeses, most nuts and seeds. For vegetables, mostly the leafy and green ones, such as lettuce, spinach, wild greens, courgette and broccoli.

Bread, pasta, rice and other grains are high in carbohydrates. So are sugar and sweets, potatoes, most fruit, sugary soft drinks and juices. These you usually cut out, or eat in very small amounts.

Dairy needs a little care. Milk contains lactose, a natural sugar, so it goes in only in small amounts. Cream and plain strained yoghurt fit more easily; yoghurts with fruit or sugar usually do not. Always check the label too, because sauces, cured meats and ready meals can hide sugar or starch.

Most fruit contains quite a lot of natural sugar. With a limit that is usually under 20–50 grams of net carbs a day, one large sweet fruit can use up a big part of it. That is why fruit goes in rarely on keto, and in small amounts.

Berries fit more easily, such as strawberries, blackberries and raspberries, which are usually lower in carbohydrates than most fruit. Avocados and olives are fruits too, botanically speaking, only they are high in fat and low in carbohydrates; they suit keto well. Lemon and lime are easy to use for flavour.

Juices, dried fruit and fruit in syrup are best left alone, because they pack a lot of sugar into a small amount. Bananas, grapes and figs are also very sweet.

Bread, pasta and rice are high in carbohydrates, but you can often swap them for vegetables. Grated cauliflower becomes “rice”, while boiled and mashed it becomes a mash. Courgette, cut into thin strips, becomes “spaghetti”.

For bread, crackers and doughs, the usual choice is almond or coconut flour, ground flaxseed and psyllium, together with eggs and cheese. Almond flour has more calories than wheat flour, though, so watch how much you use.

With ready-made products that say “low-carb”, read the label carefully, because some contain starch, wheat flour or maltitol. Most of the time the simplest thing is a salad or cooked vegetables on the side.

Sugar, honey and syrups are high in carbohydrates. On keto they are usually replaced by stevia, which is very sweet in tiny amounts, and by polyols such as erythritol and xylitol. Polyols are listed under carbohydrates on the label. Since most of them barely raise blood glucose, though, we subtract them when we work out net carbs.

Erythritol has almost zero calories and raises neither glucose nor insulin. In large amounts it can upset the stomach, however. Recent studies are looking at whether a lot of erythritol affects the heart; it is not yet clear, so it is best used in moderation. Maltitol is a different story: it raises glucose noticeably, so a product made with it has a bigger effect than its net carbs suggest.

If you have a dog, keep xylitol away from it, because it is toxic to dogs. And if you have diabetes, talk to your doctor before you change your diet.

Mostly, yes. Olive oil, olives, feta, grilled meat and fish, eggs, salads and greens are low in carbohydrates and fit without any trouble. Grilled fish with boiled greens and olive oil is a keto dish exactly as it is served.

With ladera, vegetables slow-cooked in olive oil, look at what else is in the pot. Potato, rice and a lot of tomato raise the carbohydrates. Green beans or courgettes without potato fit more easily, in a sensible portion. Stuffed vegetables (gemista) and filo pies are high in carbohydrates from the rice and the pastry; in our recipes the gemista are made with cauliflower in place of the rice.

Pulses (lentils, beans, chickpeas) are nutritious, but fairly high in carbohydrates. On strict keto they usually stay out, or go in only in very small amounts. The same goes for the bread and potatoes that often come with a Greek meal.

The ketogenic diet is not for everyone. Before you change your diet in a big way, talk to your doctor, especially if you have type 1 or type 2 diabetes or take insulin or other diabetes medication: there is a risk of hypoglycaemia and ketoacidosis. The same goes if you take medication for blood pressure or the heart, or any other long-term treatment.

Ask your doctor first in these cases too: a kidney, liver, pancreas or gallbladder condition; pregnancy, trying to conceive or breastfeeding; an eating disorder, now or in the past; being under 18.

Do not change or stop any medication without asking your doctor. With some medicines the dose may need adjusting when your diet changes; only the doctor who looks after you can decide that.

It is what people call the tiredness, headache, dizziness or cramps that some feel in the first days of keto. It is not flu at all. It comes mainly from the water and salts the body loses.

With few carbohydrates you lose more electrolytes in your urine, minerals such as sodium, potassium and magnesium. If you drink enough fluids and top up your electrolytes, the symptoms usually go within a few days.

If they are severe or do not pass, stop and see a doctor. When you have diabetes or take medication that lowers blood glucose, dizziness and feeling unwell can mean hypoglycaemia; then you follow your doctor’s instructions. With a kidney or heart condition, or if you take medication (especially for blood pressure), ask your doctor before you take electrolyte supplements. For an urgent medical problem, call 112.

No, they are two very different states. Ketosis is the state the ketogenic diet aims for: with very few carbohydrates the body burns mainly fat, and the liver makes ketones as an alternative fuel.

Ketoacidosis is dangerous. Ketones rise far too high and the blood becomes acidic. It is seen mainly in type 1 diabetes, and more rarely in type 2 with certain medicines. It can show up as intense thirst, frequent urination, nausea or vomiting, abdominal pain and fast breathing. It needs immediate medical care.

If you have type 1 or type 2 diabetes, talk to your doctor before starting keto, because there is a risk of hypoglycaemia and ketoacidosis. For an urgent medical problem, call 112.

Electrolytes are minerals such as sodium, potassium and magnesium. They regulate the body’s fluids, nerves and muscles. On keto, especially in the first days, you lose more water in your urine and more electrolytes with it. When you run short, you may feel tired or dizzy, or get headaches or cramps.

So drink enough fluids and do not cut out salt completely, unless your doctor has told you to limit fluids or salt. You get potassium and magnesium from leafy green vegetables, avocado, nuts and seeds, all of which fit keto.

Electrolyte supplements are not something to take blindly. If you have a kidney or heart condition or take medication, especially for blood pressure, ask your doctor first; too much can be dangerous as well.

Intermittent fasting means you eat only at certain hours of the day, for example 16 hours of fasting and 8 hours of eating. Many people combine it with keto, but it is not required; keto works just as well with regular meals.

If you want to try it, it is usually easier once you are used to keto than from day one. During your eating hours, put enough protein and vegetables into your meals. Water you keep drinking during the fasting hours too.

It is not for everyone. If you have diabetes or take medication that lowers blood glucose, are pregnant or breastfeeding, have or have had an eating disorder, or are under 18, ask your doctor first. And if you feel unwell, stop fasting and see a doctor.

When you cut out bread, grains, pulses and most fruit, you may eat less dietary fibre than before. Some people become constipated as a result, mostly at the start. Fibre helps the gut and keeps you full; since it does not raise blood glucose, it does not count towards net carbs.

Leafy vegetables, broccoli, cauliflower, courgettes and avocado give you fibre with few net carbs, and so do nuts, and seeds such as flaxseed and chia. Drink enough fluids as well, since on keto you lose more water.

If constipation lasts for many days, talk to your doctor. With severe abdominal pain, blood in the stool or vomiting, get medical help straight away; for an emergency, call 112. Ask your doctor before you take laxatives or fibre supplements, especially if you take medication.

Yes, generally. In the first weeks, until your body gets used to burning mainly fat, you may tire more quickly or perform less well, especially in hard exercise. So start gently and build up the intensity bit by bit.

Sweat takes water and salts with it, and on keto you already lose more of those in your urine. Drink enough fluids and keep an eye on your electrolytes, especially when it is hot. You also need enough protein, because your muscles depend on it.

If you have diabetes or take medication that lowers blood glucose, exercise combined with few carbohydrates can raise the risk of hypoglycaemia. In that case, or with a heart condition, talk to your doctor first. If you feel dizzy or unwell, stop exercising and see a doctor. For chest pain or any other emergency, call 112.

Not in the first year. Ola Keto started out to explain things and work them out: articles, guides, recipes, foods and calculators. It is not a tracking app.

A log would mean keeping daily health data for every member, which is a big responsibility. We will look at it again as the site grows. Until then, the tools do the maths on your device. Only the result is saved, and only if you ask.