Ketogenic diet: complete guide to the eating strategy that transforms your metabolism
The ketogenic diet, or simply keto, is an eating plan that is low in carbohydrates, rich in healthy fats, and moderate in protein. Unlike classic low-calorie diets, keto does not rely on calorie counting, but rather on changing the primary energy source: from glucose to fats.
Its name comes from ketosis, a natural metabolic state in which the body, not having enough sugars to burn, begins to produce ketone bodies from fats. And these ketones become the main fuel.
How metabolism works in ketosis
Under normal conditions, the body uses glucose (derived from carbohydrates) to produce energy. However, when carbohydrate intake is drastically reduced (below 50 g net per day), hepatic and muscle glycogen stores are depleted in 1–3 days. At that point, the liver begins to:
- convert fatty acids into ketone bodies (β-hydroxybutyrate, acetoacetate, acetone)
- send them into the bloodstream as a new energy source
- fuel the brain, muscles, heart, and peripheral tissues without the need for sugar
This process, called ketogenesis, is the basis of the weight loss, appetite reduction, and blood sugar stabilization observed in the keto diet.
The main benefits of the ketogenic diet
1. Real and sustainable weight loss
- Promotes lipolysis (use of stored fats)
- Eliminates water retention caused by carbohydrates
- Reduces appetite and hunger pangs
2. Glycemic and insulin control
- Maintains stable blood sugar levels
- Reduces insulin, promoting fat burning
- Can help in cases of insulin resistance, type 2 diabetes, PCOS
3. Cognitive benefits
- Ketones fuel the brain continuously with less "energy crash"
- Many report increased concentration, clarity, less mental fog
4. Anti-inflammatory effect
- Reduction of inflammatory markers (CRP, IL-6)
- Positive effect in autoimmune diseases, chronic inflammatory conditions, and joint pain
5. Therapeutic effects in clinical settings
- Used for decades in the treatment of refractory epilepsy
- Emerging studies on Alzheimer's, Parkinson's, migraines, brain tumors
What do you eat on a ketogenic diet?
The ketogenic diet is based on foods rich in healthy fats, quality protein sources, and low-carbohydrate vegetables.
Allowed foods
- Fats: extra virgin olive oil, butter, ghee, coconut oil, avocado
- Protein: meat, fish, eggs, aged cheeses
- Low-carb vegetables: zucchini, cauliflower, spinach, mushrooms, cucumbers
- Low-carb fruits: avocado, olives, berries in controlled amounts
- Drinks: water, coffee, green tea, herbal teas
Foods to avoid
- Bread, pasta, rice, cereals, potatoes
- Sweets, cookies, snacks, sugary drinks
- Sugary fruits (bananas, apples, grapes, mango)
- Legumes (beans, lentils, chickpeas)
- Ultra-processed industrial products
How are macronutrients distributed?
A classic ketogenic diet includes:
| Macronutrient | Percentage | Function |
|---|---|---|
| Fats | 70–75% | Primary energy source |
| Proteins | 20–25% | Muscle mass maintenance |
| Carbohydrates | 5–10% | (<50g net/day) |
Net carbohydrates are calculated as: Total carbohydrates – Fiber – Polyols (if present)
Possible side effects and adaptation
“Keto flu”
This is a transitional phase during which fatigue, headaches, irritability, nausea, and difficulty concentrating may occur.
Remedies: increase electrolyte intake (sodium, magnesium, potassium), drink plenty of water, avoid intense workouts in the first few days.
Other effects
- Keto breath: temporary fruity odor
- Constipation: compensate with fiber from vegetables and water
- Menstrual changes or irregular periods: temporary, related to adaptation
Is it suitable for everyone?
The ketogenic diet is not a universal diet. It is important to consult a professional to determine if it is compatible with your physical and clinical condition.
Contraindications
- Pregnancy and breastfeeding (unless medically indicated)
- Advanced kidney and liver disease
- Eating disorders (past or present)
- Use of hypoglycemic medications: supervision required
What does science say?
- Type 2 Diabetes: improved insulin sensitivity and reduced medication
- Obesity: greater effectiveness compared to standard low-calorie diets in the first 6 months
- Neurology: documented efficacy in epilepsy control and promising in slowing neurodegenerative diseases
- Inflammation and metabolic markers: significant reduction in triglycerides, blood sugar, blood pressure
Sources: “Ketogenic Diet: Evidence for Optimized Fat Metabolism”, Frontiers in Nutrition; “A low-carbohydrate, ketogenic diet to treat type 2 diabetes”, Nutrition & Diabetes; “Ketone Bodies and Brain Metabolism”, Nature Reviews Neuroscience.