Science, not marketing

Our method, in full transparency

FittyFlow doesn't pull numbers out of a hat. Every recommendation rests on validated equations and official nutrition references. Here's exactly how we compute your guidance — enough to reassure any dietitian, nutritionist or fitness coach.

Your basal metabolic rate (BMR)

We calculate what your body burns at rest with the Mifflin-St Jeor equation, the most accurate one validated for the general population. It accounts for your sex, age, height and weight — not an anonymous average.

BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + (5 M / −161 F)

Your total daily expenditure (TDEE)

We multiply your BMR by your real activity level (PAL): sedentary, light, active or athletic. That's the energy you actually spend in a day.

TDEE = BMR × PAL (1.2 to 1.725)

Your calorie target (safe deficit)

To lose fat without burning out, we apply a moderate deficit based on your pace (12 to 25%), always bounded by a safety floor. We never go below official references — too aggressive a deficit melts muscle and guarantees the yo-yo effect.

Target = max(TDEE − deficit, safety floor)

Your macronutrients

We first set a high protein intake (1.6 to 2.2 g/kg of target weight) to preserve your muscle mass in a deficit, then enough fat for your hormones, and carbs as fuel. It's the most overlooked variable in diets — and the most decisive.

Protein 1.8 g/kg · Fat 0.9 g/kg · Carbs as remainder

Your progress, continuously adjusted

We analyze your real weight curve with linear regression to detect a plateau. When weight stalls, we tighten the deficit or vary activity — just as a practitioner would in consultation. On the fitness side, the load increases gradually (progressive overload).

Trend = slope of weigh-ins over 4 weeks

🛡️ Our safeguards

• Never a target below the safety floor (≥ 1200 kcal women / 1500 kcal men).
• Loss capped at ~1% of body weight per week (healthy, sustainable loss).
• Protein first to preserve muscle mass, not just the number on the scale.
• No prolonged fasting, no “miracle” diet, no demonizing of foods.
• Educational tool: it does not replace a health professional.

Scientific sources

The foundations of our calculations, in plain terms.

Mifflin-St Jeor
Mifflin MD, St Jeor ST, et al. « A new predictive equation for resting energy expenditure in healthy individuals », Am J Clin Nutr, 1990.
Besoins protéiques
Helms ER, et al. « Evidence-based recommendations for natural bodybuilding contest preparation », J Int Soc Sports Nutr, 2014 (1,6–2,2 g/kg en déficit).
ANSES
ANSES, « Actualisation des repères du PNNS : références nutritionnelles », 2016 (apports de sécurité, fibres, hydratation).
OMS
Organisation mondiale de la Santé, classification de l'IMC et recommandations d'activité physique (2020).
Surcharge progressive
American College of Sports Medicine, « Progression Models in Resistance Training for Healthy Adults », Med Sci Sports Exerc, 2009.

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