What Is the Ketogenic Diet?
The ketogenic diet is a very low-carbohydrate, high-fat diet that shifts the body into a metabolic state called ketosis. In ketosis, the liver converts fatty acids into ketone bodies, which the brain and muscles use as fuel instead of glucose. This metabolic switch is the defining characteristic that separates keto from other low-carb diets.
The standard keto macro ratio is approximately 70% fat, 25% protein, and 5% carbohydrates. This calculator defaults to these ratios but allows adjustment within keto-safe bounds so you can customise your protocol while staying in the fat-adaptive metabolic zone.
How Ketosis Works
Under normal dietary conditions, glucose from carbohydrates is the body's preferred fuel. When carbohydrate intake drops below approximately 50g/day, blood glucose and insulin levels fall. With insufficient glucose available, the liver begins breaking down stored fat into ketone bodies (beta-hydroxybutyrate, acetoacetate, and acetone), which circulate in the blood and are used as fuel by most tissues, including the brain.
The adaptation period — when the body transitions from glucose to fat/ketone metabolism — typically takes 2–4 weeks. During this time, some people experience the “keto flu”: fatigue, headaches, brain fog, and irritability. These symptoms resolve as the body becomes fat-adapted and can usually be mitigated by ensuring adequate electrolyte intake (sodium, potassium, magnesium).
Net Carbs: The Number That Matters
Net carbs = Total dietary carbohydrates − Dietary fibre. Dietary fibre is not digested or absorbed for energy and does not raise blood glucose, so it does not affect ketosis. Most practitioners target under 25–30g of net carbs daily to maintain ketosis consistently.
This calculator tracks both total carbs and net carbs so you have a complete picture of your carbohydrate intake. Foods with high fibre content (leafy greens, broccoli, chia seeds) have a much lower net carb count than their total carb count suggests, making them particularly useful on a keto diet.
Keto Macro Ratios Explained
- Fat (60–80%, default 70%): The primary fuel source. Fat must be high enough to provide adequate calories while keeping protein and carbs within keto bounds. Sources: fatty meats, oily fish, butter, olive oil, avocado, cheese, nuts.
- Protein (15–30%, default 25%): Moderate to prevent excess gluconeogenesis (conversion of amino acids to glucose). Sources: beef, chicken thigh, eggs, pork, fish, dairy.
- Carbohydrates (3–10%, default 5%): Kept very low to maintain ketosis. Focus entirely on fibrous vegetables. Sources: leafy greens, broccoli, cauliflower, zucchini, asparagus.
Benefits and Limitations
Research demonstrates keto diets can produce faster initial weight loss (partly from water loss as glycogen is depleted), reduce blood triglycerides, raise HDL cholesterol, and significantly improve blood sugar control in type 2 diabetes patients. Some people report reduced hunger and improved mental clarity once fat-adapted.
Limitations include difficulty sustaining the diet socially, reduced exercise performance (particularly for high-intensity activities), potential for nutrient deficiencies if vegetable variety is low, and the requirement for ongoing careful carb tracking to maintain ketosis. Long-term adherence studies show keto diets have similar outcomes to other calorie-controlled diets at 12 months.