Keto Diet: The Complete Guide

What is a keto diet?

A keto diet (or ketogenic diet) is an eating pattern built around three principles: very few carbohydrates, a moderate amount of protein, and a lot of fat. Concretely, a typical keto diet consists of 70 to 75 percent of calories from fat, 20 percent from protein and only 5 to 10 percent from carbohydrates — often a maximum of 20 to 50 grams of net carbohydrates per day.

For comparison: the average Dutch diet consists of around 45 percent carbohydrates (200-250 grams per day). The goal of keto is to bring the body into a metabolic state called ketosis, in which fat — not glucose — becomes the primary fuel for both muscles and brain.

The ketogenic diet was originally developed in the 1920s as a treatment for therapy-resistant epilepsy in children. Only in the past 15 years has it become popular as a weight loss strategy, partly thanks to well-known advocates and clear short-term results.

How does ketosis work biochemically?

Normally your body uses glucose (from carbohydrates) as fuel. If you drastically restrict carbohydrates, your glycogen stores in liver and muscles are depleted within 24 to 72 hours. The body then switches to fat burning.

During fat burning, the liver produces ketones (acetoacetate, beta-hydroxybutyrate and acetone) as an alternative fuel. Brain, heart and muscles can use these ketones effectively. When the ketone level in the blood rises above 0.5 mmol/L, you are officially in ketosis.

Many people only reach ketosis after 5 to 14 days of strict carbohydrate restriction. Ketosis can be measured with urine strips (cheap but inaccurate), a blood meter (most reliable) or a breath meter (convenient).

What can you eat on keto?

The keto plate looks fundamentally different from a traditional Dutch plate. Meat, fish, eggs, cheese and green vegetables form the basis. Bread, pasta, rice, potatoes and most types of fruit disappear.

• Yes: meat (red, chicken, pork), fish (especially oily fish such as salmon, mackerel), eggs, hard and soft cheese, butter, olive oil, coconut oil, avocado, nuts and seeds, green leafy vegetables (spinach, lettuce, kale), broccoli, cauliflower, courgette, asparagus, mushrooms, berries (small portion).
• Limited: berries, tomatoes, peppers, onion (all in small amounts because of carbohydrates).
• No: bread, pasta, rice, potatoes, sugar, sweets, fruit (except berries), legumes (beans, lentils, chickpeas), milk and yoghurt, beer and wine with residual sugar, soft drinks, fruit juice, most sauces and dressings.

Scientific evidence for weight loss

Meta-analyses show that keto delivers 2 to 5 kilograms more weight loss in the first 3 to 6 months than a calorie-restricted low-fat diet. This is largely due to loss of glycogen (3-4 grams of water per gram of glycogen) and better satiety from protein and fat.

In the long term (12 months or longer), however, this advantage largely disappears. In randomised studies, long-term results come out at a comparable weight loss to a balanced Mediterranean or protein-rich diet — both around 4 to 7 percent of starting weight after a year.

The real advantage of keto turns out to be satiety: participants spontaneously eat less because ketones and high protein intake suppress appetite. People with type 2 diabetes or prediabetes also show clear improvements in HbA1c and fasting glucose.

Benefits of keto

Besides weight loss, keto has shown some specific benefits in studies.

• Rapid initial weight loss (motivating in the first weeks).
• Improved glucose regulation and HbA1c in type 2 diabetes (medication reduction often possible).
• Lower triglycerides and higher HDL cholesterol in many studies.
• Satiety from protein and fat: less hunger between meals.
• More stable energy without the typical afternoon glucose dip.
• Therapeutic value in specific conditions: refractory epilepsy, some neurological diseases, PCOS.

Drawbacks and risks

Keto has clear drawbacks that make it hard for many people to maintain.

• Socially difficult: restaurants, parties and family dinners become challenging.
• High drop-out rate: around 50% stop within 6 months, 70-80% within a year.
• LDL cholesterol rises significantly in some people (genetically determined, a check beforehand is wise).
• Risk of kidney stones due to increased protein and oxalate intake.
• Fibre deficiency and possible constipation without deliberate fibre supplementation (seeds, nuts).
• Vitamin and mineral deficiencies (especially B vitamins, vitamin C, magnesium, potassium) with poorly planned keto.
• Yo-yo effect: when carbohydrates are resumed, weight often returns quickly due to the glycogen and water effect.

The keto flu

The keto flu is a set of complaints that typically occurs on days 3 to 7 of a strict keto diet. The cause is a combination of glucose withdrawal, fluid shortage (glycogen binds a lot of water) and electrolyte loss.

Typical symptoms are headache, fatigue, irritability, insomnia, muscle cramps, dizziness and difficulty concentrating. Women more often report nausea and palpitations than men.

Solution: extra salt daily (3 to 5 grams extra), potassium-rich food (avocado, spinach, mushrooms), magnesium supplementation (300 to 400 mg), drinking enough (2.5 to 3 litres of water). The complaints usually disappear within 7 to 10 days.

Keto recipes and weekly plan

A typical keto day looks roughly like this: breakfast of fried eggs in butter with avocado and bacon (no bread); lunch of salad, grilled chicken, olive oil and feta; dinner of salmon, roasted broccoli and cauliflower rice; snacks of macadamia nuts and olives.

Practical keto recipes that are popular: cauliflower rice bowls, courgette pasta with bolognese sauce without pasta, chicken skewers with avocado dressing, omelettes with mushrooms and cheese, fat bombs (chocolate-nut truffles) as a snack.

Meal prepping is important: keto requires preparation because many ready-made meals contain too many carbohydrates. Plan 2 to 3 cooking sessions per week and make sure keto snacks are ready for unexpected hunger.

Keto versus GLP-1 medication

Both approaches work via appetite regulation, but in fundamentally different ways. Keto suppresses appetite via high protein/fat intake and the effect of ketones on the brain. GLP-1 medication (Ozempic, Wegovy, Mounjaro) suppresses appetite via direct receptor activation in the stomach, intestines and hypothalamus.

For most people GLP-1 medication is more sustainable: you can continue to eat normally, social situations are easier, and the effect on appetite is stronger and more consistent. Studies show 15 to 22 percent weight loss over 12 to 18 months — significantly more than keto in the same period.

The combination of keto + GLP-1 is technically possible but rarely necessary. For users who still want both, we recommend a mildly low-carb approach (50-100 grams per day) instead of strict keto, because appetite on GLP-1 is already low and strict keto can increase the risk of malnutrition.

Who is keto (not) suitable for?

Keto may be suitable for: people with type 2 diabetes (under supervision, often with medication adjustment), people with therapy-resistant epilepsy (the classic indication), athletes with specific endurance goals, and people who want to lose a lot of weight in a short time for a specific goal.

Keto is NOT suitable or is risky in: type 1 diabetes (risk of diabetic ketoacidosis), chronic kidney disease (too much protein), gallstones or pancreatitis (too much fat can trigger these), pregnancy or breastfeeding (possible effects on foetal development), a history of eating disorders (restriction can trigger relapse), and in children except under medical epilepsy supervision.

If in doubt: always discuss keto with a doctor or dietitian beforehand, especially if you take medication or have a chronic condition.

Practical tips for beginners

Start with a 2-week transition period in which you gradually reduce carbohydrates. This lowers the chance of a severe keto flu.

Invest in a macro-tracking app (Carb Manager, MyFitnessPal) for the first 4 to 6 weeks. Many people underestimate hidden carbohydrates in sauces, ready-made products and vegetables such as carrots and beetroot.

Plan electrolytes from day 1: extra salt on food, a magnesium supplement in the evening, potassium-rich vegetables daily. This prevents 80 percent of keto flu complaints.

Have a 'cheat plan': what do you do at a birthday or dinner invitation? A 'lazy keto' approach (only counting carbohydrates, not logging everything) is more sustainable for many people than strict keto.

Test your cholesterol after 3 months. If LDL rises significantly, you can switch to a Mediterranean variant with more unsaturated fat (olive oil, fish, nuts) and less saturated fat (butter, fatty meat).