Calculatrice de Macros Keto

A ketogenic macro split is defined by one constraint and one target: carbohydrate low enough to shift the body towards ketone production, and protein high enough to preserve lean mass without being so high that it undermines the first goal. Fat then fills the remaining energy. This calculator sets protein from lean body mass rather than total weight, which is the more defensible approach and the reason it asks for body fat percentage.

La formule

Lean body mass = weight x (1 - body fat % / 100)
BMR (Katch-McArdle) = 370 + (21.6 x lean body mass in kg)
TDEE = BMR x activity factor
Protein = 0.6 to 1.0 g per lb of lean mass
Carbohydrate = fixed limit, commonly 20 to 50 g/day
Fat = remaining calories / 9

• Protein and carbohydrate provide 4 calories per gram, fat 9
• The Katch-McArdle equation uses lean mass, so it needs a body fat estimate but handles muscular and lean bodies better than weight-based equations

Katch-McArdle basal metabolic rate equation. Carbohydrate thresholds for nutritional ketosis follow the range used in the clinical and research literature rather than a single defined cut-off.

How the numbers are derived

Basal metabolic rate is estimated from lean body mass, because muscle and organ tissue account for nearly all resting energy expenditure while fat tissue accounts for very little. That is why the Katch-McArdle equation is preferred here over weight-based equations such as Mifflin-St Jeor: two people at the same weight with different body composition have genuinely different resting requirements.

Protein is then set per pound of lean mass rather than total weight, for the same reason. Setting protein from total weight overshoots substantially in people carrying more fat, and overshooting protein matters on a ketogenic diet because surplus amino acids can be converted to glucose.

Carbohydrate is a fixed ceiling rather than a percentage, which is the part people most often get wrong. A percentage-based carbohydrate target scales with total intake, so a large eater on "5 percent carbs" can exceed the ketogenic threshold in absolute grams while believing they are compliant.

Typical targets

The ranges below are those in common use. There is no single validated threshold for nutritional ketosis, and individual carbohydrate tolerance varies with activity, muscle mass and insulin sensitivity.

• Net carbohydrate normally means total carbohydrate minus fibre, and in some conventions minus sugar alcohols. The convention used changes the number substantially.
• Fat is what fills the gap. Eating fat beyond that gap does not deepen ketosis; it simply adds calories.

Adaptation and common problems

The first one to two weeks commonly bring headache, fatigue, irritability, muscle cramps and poor exercise tolerance. Most of this is not the absence of glucose but the loss of sodium and water: lowering carbohydrate lowers insulin, which increases renal sodium excretion, and fluid follows. Deliberate sodium, potassium and magnesium intake addresses most of these symptoms directly.

Constipation is the other frequent complaint, and it usually reflects the loss of fibre-bearing foods rather than the diet itself. Low-carbohydrate vegetables, nuts and seeds keep fibre intake reasonable without threatening the carbohydrate ceiling.

Limites

• The calculation depends on a body fat estimate, which is itself uncertain. Consumer bioimpedance scales commonly err by several percentage points, and that error propagates into every downstream figure.
• BMR equations estimate a population average. Individual resting energy expenditure varies around any equation by roughly 10 percent even when lean mass is known accurately.
• There is no single carbohydrate threshold for ketosis. Individual tolerance varies with activity, muscle mass and insulin sensitivity.
• Ketogenic diets are used clinically for drug-resistant epilepsy under supervision. Self-directed use for other purposes has a much weaker evidence base, and long-term data are limited.
• They are not appropriate for people with type 1 diabetes without close supervision, for those on SGLT2 inhibitors because of ketoacidosis risk, in pregnancy, or with pancreatitis, liver failure or certain rare metabolic disorders.
• Anyone taking insulin or sulfonylureas needs medication adjustment before reducing carbohydrate, because hypoglycaemia risk rises sharply.

Questions fréquentes

How many carbs can I eat on keto?

Commonly 20 to 50 grams of net carbohydrate a day, with the lower end used for induction. There is no single validated threshold, and individual tolerance varies with activity level, muscle mass and insulin sensitivity.

Why does this calculator ask for body fat percentage?

Because it sets both metabolic rate and protein from lean body mass rather than total weight. Muscle and organ tissue drive resting energy expenditure while fat tissue contributes little, so two people at the same weight with different composition have different requirements.

Can I eat too much protein on keto?

Excess protein can be converted to glucose, which is why targets are set per pound of lean mass rather than total weight. In practice, moderate protein at 0.6 to 1.0 g per pound of lean mass preserves muscle without undermining ketosis for most people.

What causes keto flu?

Mostly sodium and fluid loss rather than lack of glucose. Lower carbohydrate means lower insulin, which increases renal sodium excretion, and water follows. Deliberate sodium, potassium and magnesium intake resolves most of the symptoms.

Do I need to hit my fat target exactly?

No. Fat is the balancing item that fills remaining calories, not a goal in itself. Eating beyond that does not deepen ketosis, it just adds energy, which matters if the aim is weight loss.

Références

1. Masood W, Annamaraju P, Uppaluri KR. The Ketogenic Diet: Clinical Applications, Evidence-based Indications, and Implementation. StatPearls, NCBI Bookshelf.
2. National Academies. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. NCBI Bookshelf.
3. MedlinePlus. Carbohydrates.
4. MedlinePlus. Dietary fats.