Keto diet: how ketosis works and what you can eat

Keto means very few carbs – usually under 50 g a day – and lots of fat, so your liver makes ketones. Food list, example day and who should check first.

Keto – short for ketogenic diet – swaps most carbs for fat. It’s one way of eating among many, not a must: what matters for your energy balance is how much you eat over the day, not the split between fat and carbs. If keto suits you, here’s how it works and what goes on the plate.

How ketosis works

Your body normally runs mainly on glucose from carbohydrates. When you eat very few carbs – usually 20 to 50 g a day – and lots of fat, your liver turns fatty acids into ketones. They become an important source of energy, for the brain too. This state is called ketosis.

Check with your doctor first. If you have diabetes, a very low-carb diet can bring your blood glucose down sharply – with insulin or glucose-lowering tablets there’s a risk of hypos. Only switch with medical support. Whether keto is suitable during pregnancy, with kidney disease or with an eating disorder is still unclear.

Keto food list: what fits and what doesn’t

The basics

• Fats and oils: olive oil, coconut oil, avocado oil, butter, ghee.
• Protein: meat, oily fish (salmon, herring), eggs.
• Full-fat dairy: cheese, cream, Greek yoghurt.
• Above-ground veg: spinach, kale, broccoli, cauliflower, courgette, avocado.
• Snacks: macadamias, pecans, walnuts, almonds.

Doesn’t fit (lots of carbs)

• Grains: bread, pasta, rice, oats, muesli, corn.
• Sweet things: sugar, honey, cake, chocolate.
• Most fruit: bananas, apples, oranges, mangoes (small amounts of berries are fine).
• Starchy veg: potatoes, sweet potatoes, larger amounts of carrots.
• Pulses: lentils, chickpeas, beans.

Keto example day

A classic keto day with around 20 g of net carbs (carbs minus fibre):

• Breakfast: two fried eggs cooked in butter or ghee, half an avocado, coffee with cream – no added sugar.
• Lunch: a big salad with chicken breast, olives, macadamias and an olive oil dressing.
• Dinner: beef steak or salmon with green beans in butter – without a side like potatoes. For more room with carbs, see low-carb.

Common mistakes: eating too little veg, not drinking enough, and starting keto without talking to your doctor while you take medication for blood glucose or blood pressure.

Keto recipes: everyday recipes with very few carbs

Frequently asked questions

What is keto flu?

In the first days of switching, some people get headaches, tiredness, dizziness or feel irritable. At first the body loses a lot of water and salts. Drink enough – and if you have high blood pressure, heart or kidney problems, talk to your doctor before adding more salt.

Can you build muscle on keto?

Yes, if you eat enough calories and enough protein and do regular strength training. Better sports performance on keto hasn’t been shown, according to the German Nutrition Society’s position paper on sports nutrition.

Is keto bad for your kidneys?

Keto is high in fat rather than high in protein. Whether it suits people with kidney disease is unclear, though – then only after talking to your doctor.

How many carbs can you eat on keto?

Usually 20 to 50 g a day. Where you need to be to stay in ketosis differs from person to person – many start at around 20 g of net carbs and keep to vegetables that grow above ground.

Sources

1. diabinfo – German Diabetes Information Portal (Helmholtz Munich, German Diabetes Center, German Center for Diabetes Research): Ernährungsformen (in German). https://www.diabinfo.de/leben/diabetes-im-alltag/ernaehrungsformen.html