Macro & TDEE Calculator (Protein, Carbs, Fats)

The Mathematics of Metabolism

Weight management is not magic; it is physics. Before you begin, it is helpful to know your starting point by checking your BMI Score to understand your general health category. Once you have a baseline, we apply the First Law of Thermodynamics.

At Fitness AI, we utilize the Mifflin-St Jeor Equation to calculate your Basal Metabolic Rate (BMR). If you are combining this with exercise, ensure you are tracking your Heart Rate Zones to maximize your calorie burn efficiency.

Understanding TDEE Components

Your Total Daily Energy Expenditure (TDEE) is a dynamic number composed of four key elements:

BMR (Basal Metabolic Rate): ~70% of total burn. This is the energy required to keep your heart beating, lungs breathing, and brain functioning while at complete rest.
NEAT (Non-Exercise Activity Thermogenesis): ~15% of total burn. The energy used for walking, typing, fidgeting, and standing. This is the most variable component and often the key to fat loss.
TEF (Thermic Effect of Food): ~10% of total burn. The energy required to digest food. Protein has the highest TEF (20-30%), meaning you burn more calories simply by digesting protein compared to fats or carbs.
EAT (Exercise Activity Thermogenesis): ~5% of total burn. The calories burned during deliberate exercise like lifting weights or running.

Deep Dive: Macronutrients

While calories determine your weight, Macronutrients determine your body composition (Muscle vs. Fat ratio). Our algorithm prioritizes muscle retention.

Protein: The Architect

Protein is essential for muscle protein synthesis (MPS). During a calorie deficit, the body is prone to breaking down muscle tissue for energy. To prevent this, Fitness AI sets your protein target high (approx. 2g per kg of body weight).
Best Sources: Chicken breast, white fish, lean beef, tofu, lentils, whey isolate, greek yogurt.

Fats: The Regulator

Dietary fats are precursors to essential hormones like Testosterone and Estrogen. Extremely low-fat diets can crash your libido and mood. We ensure your fat intake never drops below 0.6g per kg of body weight to maintain hormonal homeostasis.
Best Sources: Avocado, olive oil, almonds, walnuts, salmon, egg yolks.

Carbohydrates: The Fuel

Carbs are the body's preferred source of energy for high-intensity anaerobic work (like lifting weights). Once Protein and Fat requirements are met, the remaining calories are allocated to Carbohydrates to fuel performance.
Best Sources: Rice, oats, potatoes, sweet potatoes, fruits, fibrous vegetables.

Expert Insights & FAQ

Q: What is "Reverse Dieting"?

Reverse dieting is the process of gradually increasing calorie intake after a prolonged diet. This helps restore metabolic rate (BMR) that may have slowed down due to adaptive thermogenesis, minimizing fat gain while returning to maintenance.

Q: Why is the scale not moving?

Weight loss is non-linear. Water retention from sodium, cortisol (stress), or muscle glycogen can mask fat loss. If you are in a deficit, you are losing fat. Trust the process and track weekly averages.

Q: Should I track "Net Carbs"?

Unless you are on a strict Ketogenic diet, track Total Carbs. Fiber is beneficial for digestion and satiety, but for energy balance purposes, total carbohydrate intake gives a more accurate picture.

Q: How does alcohol affect macros?

Alcohol contains 7 calories per gram but offers no nutritional value. It is often called the "fourth macro." When alcohol is present in the bloodstream, fat oxidation (burning) stops until the alcohol is metabolized.

Medical Disclaimer

This tool provides nutritional estimates based on mathematical formulas. Individual metabolism varies due to genetics, medication, and hormonal status. Consult a registered dietitian or doctor before making drastic dietary changes.

Macro Calculator & TDEE Nutrition Planner