Keto Diet for Beginners: How to Start, Set Your Macros, and Actually Enter Ketosis
The ketogenic diet is one of the most searched dietary approaches — and one of the most misapplied. Entering ketosis requires precision: carbohydrates must stay below a specific threshold that most people significantly underestimate, electrolytes must be actively managed to avoid the worst of the adaptation symptoms, and macros must be tracked with accuracy that eyeballing simply cannot provide. When keto is set up correctly from the start, the adaptation period is shorter and the results are more reliable. When it is set up on guesswork, most people either never enter ketosis or enter it briefly before unknowingly returning to glucose metabolism.
Portion control made simple – measure exactly what you need
Portion control made simple – measure exactly what you need
This guide covers exactly what keto is, how to calculate your macros, what to eat and avoid, how to handle the first week, and the tracking practices that determine whether the diet actually works.
What the Ketogenic Diet Is
Keto is a very-low-carbohydrate, high-fat dietary pattern designed to shift the body's primary fuel source from glucose to ketone bodies. Ketone bodies are produced by the liver from fatty acids when glucose availability falls below the threshold needed for normal metabolism.
Standard macronutrient breakdown:
- Fat: 70–75% of total calories
- Protein: 20–25% of total calories
- Carbohydrates: 5–10% of total calories — typically 20–50g net carbs per day
Net carbs = total carbohydrates minus fibre (and in some frameworks, minus sugar alcohols). Fibre is subtracted because it is not digested and does not raise blood glucose. A vegetable with 8g total carbs and 4g fibre contributes 4g net carbs.
The 20–50g threshold varies by individual. People with higher muscle mass, higher metabolic rates, or more activity may sustain ketosis at 50g net carbs; others require staying under 20g. Most beginners should target 20–30g net carbs until they confirm they are in ketosis, then experiment with the upper boundary.
How Ketosis Works
Under normal dietary conditions, the brain and muscles run primarily on glucose derived from carbohydrates. When carbohydrate intake drops below the threshold needed to maintain blood glucose, the liver begins converting fatty acids (from dietary fat and stored body fat) into ketone bodies — primarily beta-hydroxybutyrate, acetoacetate, and acetone.
The brain, which cannot use fatty acids directly, uses ketone bodies efficiently as an alternative fuel. After 2–4 days of strict carbohydrate restriction and initial glycogen depletion, blood ketone levels rise into the nutritional ketosis range (0.5–3.0 mmol/L). This metabolic state is what the ketogenic diet aims to maintain.
It takes 2–7 days to enter ketosis after starting keto, depending on starting glycogen stores, activity level, and how strictly carbohydrates are restricted. A single high-carb meal can kick the body out of ketosis and restart the adaptation clock.
The First Week: Keto Flu and How to Manage It
The first 3–7 days of keto are the most difficult for most beginners. As glycogen is depleted (each gram of glycogen is stored with ~3g of water), substantial water weight is lost — typically 1.5–3kg in the first week. This rapid water loss takes electrolytes with it, particularly sodium, potassium, and magnesium, producing a cluster of symptoms known as "keto flu":
- Headache (most common — primarily sodium depletion)
- Fatigue and low energy
- Brain fog and difficulty concentrating
- Muscle cramps (potassium and magnesium depletion)
- Irritability
- Nausea
These symptoms are not unavoidable — they are primarily the result of inadequate electrolyte replacement. Proactive electrolyte management prevents most keto flu:
- Sodium: 3,000–5,000mg per day (significantly higher than standard recommendations). Add salt to food liberally; drink salted water or broth.
- Potassium: 2,000–3,500mg per day. Avocado, spinach, and salmon are high-potassium keto foods.
- Magnesium: 300–500mg per day. Dark leafy greens, nuts, seeds; supplementation is often necessary.
Most people who experience severe keto flu are simply under-salting their food. Increasing sodium intake in the first week dramatically reduces adaptation symptoms.
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Real-time nutrition tracking syncs with Apple Health, Fitbit, and more
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Setting Up Your Keto Macros
Keto macro calculation follows a specific order — do not start with fat and work backwards:
- Set total calories: If weight loss is the goal, apply a 300–500 calorie deficit from your TDEE. Keto does not exempt you from calorie balance — fat loss still requires a deficit.
- Set carbohydrates: Fix at 20–30g net carbs for the first month. This is non-negotiable for entering and maintaining ketosis.
- Set protein: 1.6–2.0g per kg of bodyweight. Protein is the most important macronutrient to get right — too little causes muscle loss, too much can theoretically impair ketosis through gluconeogenesis (though this concern is often overstated; adequate protein is more important than maximising ketosis depth).
- Set fat: Fill remaining calories with fat. Fat is the variable — it adjusts up or down to hit the calorie target. It is not a minimum to hit.
Example for a 75kg person targeting fat loss:
- TDEE: ~2,200 cal; deficit target: 1,800 cal
- Carbs: 25g net × 4 cal = 100 cal
- Protein: 75kg × 1.8g = 135g × 4 cal = 540 cal
- Fat: 1,800 − 100 − 540 = 1,160 cal ÷ 9 = 129g fat
Tracking these macros accurately requires weighing food. Carbohydrate content varies dramatically within food categories (different vegetables, different brands of nuts), and the 20–50g threshold is too narrow for estimation to be reliable. A food scale with nutritional database integration is the standard tool for keto tracking — it removes the guesswork that causes most keto adherence failures.
Best Foods for Keto
| Category | Good keto options | Net carbs per 100g |
|---|---|---|
| Protein | Beef, chicken thigh, salmon, tuna, eggs, pork belly, lamb | 0g |
| Dairy | Cheddar, mozzarella, cream cheese, butter, heavy cream, Greek yogurt (plain, small amounts) | 0–4g |
| Vegetables (above ground) | Spinach, kale, broccoli, cauliflower, courgette, peppers, cucumber, lettuce | 2–6g |
| Fats and oils | Olive oil, coconut oil, avocado oil, butter, MCT oil | 0g |
| Nuts and seeds | Macadamia, pecans, walnuts, almonds, chia seeds, flaxseed | 2–8g |
| Fruit (limited) | Avocado, blackberries, raspberries (small portions) | 2–5g |
Foods to Avoid on Keto
| Food | Net carbs per typical serving | Impact |
|---|---|---|
| White rice (150g cooked) | ~55g | Exceeds full daily carb budget in one serving |
| Bread (2 slices) | ~28g | Uses the majority of the daily carb allowance |
| Banana (1 medium) | ~24g | Exceeds one day's budget for strict keto |
| Pasta (80g dry) | ~57g | Immediately breaks ketosis |
| Orange juice (250ml) | ~22g | Nearly a full day's carb allowance, with no satiety |
| Legumes (100g cooked) | ~12–20g | Half to full day's carb allowance |
Hidden carbs are the most common reason people "do keto" without entering ketosis. Sauces, dressings, processed meats, flavoured dairy, and "low-carb" packaged foods frequently contain 5–15g carbs per serving that are not accounted for without checking labels.
Tracking Carbs Accurately
Keto tracking differs from standard calorie tracking in one critical way: the margin for error is tiny. A 200-calorie miscalculation on a standard diet is inconvenient; a 15g carbohydrate miscalculation on keto can prevent or end ketosis entirely.
Practices that ensure accurate carb tracking:
- Weigh all vegetables, nuts, and dairy: These are the highest-risk foods for carb underestimation. "A handful of almonds" is 20–40g — a range of 2–4g net carbs that matters at a 20g daily limit.
- Check labels for total vs net carbs: Total carbohydrates includes fibre. Subtract fibre (and erythritol, if present) to get net carbs. Do not subtract other sugar alcohols — maltitol in particular has a significant glycaemic impact.
- Be cautious with "keto-friendly" packaged products: Marketing claims of "low-carb" or "keto-friendly" are not regulated. Check the label — many products marketed to keto dieters contain 10–15g net carbs per serving.
- Log everything including cooking oils and sauces: A tablespoon of balsamic vinegar is 4g carbs. A tablespoon of BBQ sauce is 8g. These add up quickly against a 20–30g budget.
For the full guide to using a food scale specifically for keto macro tracking, the food scale for keto guide covers the complete setup. For the broader macro counting framework (applicable across keto and other dietary approaches), the macro counting guide covers the full method.
Who Keto Works Well For
Keto tends to produce strong results for:
- People who find appetite suppression from ketosis valuable — many people report significantly reduced hunger on keto, which makes the calorie deficit easier to maintain without tracking every calorie
- Those who prefer a simple rule ("avoid all starchy foods and sugar") over portion control
- People with type 2 diabetes or insulin resistance (under medical supervision) — keto dramatically reduces blood glucose and insulin levels
- Those who enjoy high-fat foods (meat, eggs, cheese, nuts) and find protein-and-fat meals satisfying
Keto is more difficult for:
- People who train at high intensity — glycogen is the primary fuel for high-intensity exercise, and carbohydrate restriction impairs performance for most athletes at intensities above 70% VO2max
- Those with significant social eating — avoiding bread, pasta, rice, and fruit at restaurants and social occasions requires considerable planning
- People who do not enjoy fatty foods or find high-fat meals unpalatable
- Those with a history of disordered eating — the strictness of carbohydrate restriction can trigger restriction mindsets
Long-Term Sustainability
Keto produces weight loss primarily through calorie reduction (appetite suppression reduces intake) and initial water weight loss. The metabolic advantages sometimes claimed (fat adaptation, superior fat oxidation) are real but modest in size — controlled studies equating calories between keto and higher-carbohydrate diets consistently show similar fat loss outcomes over 12+ months.
The question for long-term use is adherence. A diet that produces excellent results for 3 months but is abandoned at month 4 produces worse long-term outcomes than a moderate approach maintained consistently. For the calorie deficit framework that applies across all dietary patterns, the calorie deficit guide covers how keto fits within the broader energy balance model.
Related Reading
- Food Scale for Keto: The Complete Guide to Hitting Your Macros
- How to Count Macros for Weight Loss: A Beginner's Complete Guide
- Calorie Deficit for Beginners: How to Calculate Yours and Actually Maintain It
- Best Protein Sources for Weight Loss: Ranked by Protein Per Calorie
Food Scale for Keto: The Complete Guide to Hitting Your Macros
How Much Protein Per Day: The Evidence-Based Guide to Setting Your Target
Sleep and Weight Loss: How Sleep Deprivation Blocks Fat Loss (And Why It Matters
