In This Article
Key Takeaways
- Standard keto ratio: ~70% fat, ~20% protein, ~5% carbs (by calories)
- Most people need <50g net carbs/day to achieve ketosis; strict keto targets <20g
- Protein should be set first (0.6–0.8g/lb lean mass), then carbs capped, then fat fills remaining calories
- The "keto flu" (weeks 1–2) is primarily an electrolyte issue — sodium, potassium, and magnesium
- Full metabolic adaptation to fat-burning takes 3–6 weeks, not 2–3 days
What Is the Ketogenic Diet?
The ketogenic diet is a very low-carbohydrate, high-fat diet that shifts the body's primary fuel source from glucose (from carbs) to ketone bodies (from fat). This metabolic state is called ketosis.
When carb intake drops below ~50g/day, liver glycogen is depleted within 1–2 days. The liver then converts fatty acids into ketone bodies (beta-hydroxybutyrate, acetoacetate, acetone), which the brain and muscles can use as fuel instead of glucose.
Net carbs vs. total carbs: Keto tracks "net carbs" = total carbohydrates − dietary fiber (− sugar alcohols for some). Fiber passes through largely undigested and doesn't raise blood glucose. This is why non-starchy vegetables are generally keto-friendly despite containing carbohydrates.
Standard Keto Macro Ratios
| Macronutrient | % of Calories | For 1,800 kcal diet | For 2,200 kcal diet |
|---|---|---|---|
| Fat | 70–75% | 140–150g | 171–183g |
| Protein | 20–25% | 90–112g | 110–137g |
| Carbohydrates | 5–10% | 22–45g | 27–55g |
Calorie values: Fat = 9 kcal/g, Protein = 4 kcal/g, Carbohydrates = 4 kcal/g.
How to Calculate Your Personal Keto Macros
Follow this order — protein first, carbs second, fat fills remaining calories:
Step 1: Calculate Your Calorie Target
Find your TDEE (Total Daily Energy Expenditure) using the Mifflin-St Jeor equation and your activity multiplier. Then apply your goal adjustment:
- Weight loss: TDEE − 300 to 500 kcal
- Maintenance: TDEE
- Weight gain: TDEE + 200 to 300 kcal
Step 2: Set Protein (0.6–0.8g per lb of lean body mass)
On keto, protein recommendations are slightly lower than for standard diets because excess protein can convert to glucose via gluconeogenesis and potentially inhibit ketosis. Use lean body mass (body weight minus fat mass), not total body weight:
- Sedentary: 0.6g/lb lean mass
- Active: 0.7g/lb lean mass
- Very active / athletes: 0.8g/lb lean mass
Example: 180 lb person at 25% body fat → 135 lb lean mass × 0.7 = 95g protein/day (380 kcal)
Step 3: Cap Carbohydrates
Set net carbs at 20–50g depending on your tolerance. For someone new to keto, start at 20g net carbs to ensure ketosis is achieved. More active people with higher insulin sensitivity may stay in ketosis at 50g.
At 20g net carbs: 20 × 4 = 80 kcal from carbs
Step 4: Fill Remaining Calories with Fat
Fat fills whatever calories remain after protein and carbs are accounted for:
Fat calories = Total target − Protein kcal − Carb kcal
Fat grams = Fat calories ÷ 9
Worked Example (180 lb, 25% body fat, moderately active, fat loss at 1,900 kcal/day):
- Protein: 95g × 4 = 380 kcal
- Carbs: 20g × 4 = 80 kcal
- Remaining: 1,900 − 380 − 80 = 1,440 kcal
- Fat: 1,440 ÷ 9 = 160g fat
Final macros: 160g fat / 95g protein / 20g net carbs — approximately 75% / 20% / 4% of calories.
Calculate Your Keto Macros Automatically
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Keto Variants: SKD, TKD, CKD
| Variant | Carb Protocol | Best For |
|---|---|---|
| SKD — Standard Ketogenic Diet | <50g net carbs every day | Weight loss, general health, most beginners |
| TKD — Targeted Ketogenic Diet | 25–50g carbs only around workouts | Athletes who need glycolytic capacity for HIIT |
| CKD — Cyclical Ketogenic Diet | 5 keto days + 1–2 high-carb refeed days | Experienced athletes, bodybuilders |
| High-Protein Keto | <50g carbs; protein 30% of calories | Muscle preservation during weight loss |
TKD and CKD are significantly more complex and generally not necessary for most people. SKD is appropriate for beginners and anyone focused primarily on weight loss or metabolic health rather than athletic performance.
The Adaptation Phase
Week 1–2: The Keto Flu
When carbs drop, insulin falls sharply. Low insulin causes the kidneys to excrete sodium, which takes water and other electrolytes with it. This causes the "keto flu":
- Headache, fatigue, brain fog
- Muscle cramps (magnesium and potassium loss)
- Irritability, nausea
- Rapid initial weight loss (water weight, not fat)
Prevention: supplement electrolytes aggressively in the first 2 weeks — aim for 3–5g sodium, 1–2g potassium, and 300–500mg magnesium daily. Bone broth, salt food liberally, eat potassium-rich vegetables (avocado, spinach).
Weeks 2–6: Fat Adaptation
True metabolic adaptation — the mitochondria's ability to efficiently oxidize fat — takes 3–6 weeks, not the 2–3 days often claimed. During this period, athletic performance typically decreases (especially high-intensity), energy can feel inconsistent, and cravings for carbs may fluctuate.
After 6 Weeks: Keto-Adapted State
A fully keto-adapted person experiences stable energy, reduced hunger (ketones suppress ghrelin), improved mental clarity for many people, and recovered athletic performance (at least for endurance activities). High-intensity anaerobic performance typically remains somewhat impaired without carbs.
Medical considerations: People with type 1 diabetes face DKA risk; keto requires medical supervision. Those on diabetes medications (especially SGLT2 inhibitors) need dose adjustments. People with kidney disease, gallbladder issues, or a history of pancreatitis should consult a physician before starting keto.
Frequently Asked Questions
Most people enter ketosis with 20–50g of net carbs per day (net carbs = total carbs − fiber). The standard strict keto threshold is 20g net carbs. Individual carb tolerance varies significantly — more insulin-sensitive people (active, lean) may stay in ketosis at 50–75g, while insulin-resistant individuals may need to stay under 20g. If you're uncertain, start at 20g net carbs for 2 weeks, then test using blood or urine ketone strips.
The standard keto ratio is approximately 70–75% fat, 20–25% protein, and 5% carbohydrates by calories. For a 2,000 kcal diet, this is roughly 155–165g fat, 100–125g protein, and 25g net carbohydrates. In practice, calculate protein first based on lean body mass (0.6–0.8g/lb), cap carbs at 20–50g net, then let fat fill the remaining calories — rather than hitting exact percentage targets.
Keto flu refers to symptoms during the first 1–2 weeks of keto adaptation: headache, fatigue, brain fog, irritability, muscle cramps, and nausea. It's primarily caused by electrolyte loss (sodium, potassium, magnesium) as the kidneys excrete water when insulin drops. Most symptoms resolve by day 5–10. Supplementing electrolytes proactively — especially 3–5g of sodium/day — dramatically reduces the severity and duration of keto flu symptoms.
Keto produces faster initial weight loss (2–5 lbs in the first week, mostly glycogen and water). Long-term fat loss outcomes are comparable to other approaches when calories are matched. Keto's main advantages are appetite suppression (ketones reduce ghrelin), blood sugar stabilization, and a simplified eating framework (no calorie counting needed for some). Disadvantages include the restrictive food list, social limitations, performance impacts for high-intensity athletes, and keto flu adaptation. Adherence to any sustainable approach is what matters most for long-term results.