Calories

Definition

A calorie is a unit of energy. In nutrition, we use the kilocalorie (kcal), which is the energy needed to raise 1 kg of water by 1°C. When you read "100 calories" on a label, it actually means 100 kcal.

Every food provides energy in the form of calories, which your body uses to function and move. Mastering calories is mastering body composition.

💡 The "calorie" you see on packaging = a kilocalorie (kcal). The two words are used interchangeably in everyday language.

How many calories per macronutrient?

Each macronutrient delivers a specific amount of energy:

MacronutrientEnergy per gramProtein4 kcal/gCarbohydrates4 kcal/gFats (lipids)9 kcal/gAlcohol7 kcal/gFiber~2 kcal/g

Practical takeaway: fats deliver more than twice the calories of protein or carbs per gram. That's why fatty foods are quickly calorie-dense.

Daily caloric needs

Your needs depend on your TDEE (Total Daily Energy Expenditure), which is made up of:

Average estimates per profile:

ProfileDaily needs (kcal)Sedentary woman1800-2000Active woman2000-2400Sedentary man2200-2600Active man2600-3200Heavily training athlete3000-4000+

Calories in vs. calories out

Energy balance dictates body composition:

⚠️ "Calories in vs calories out" is a real law, but the variables on each side are not constant. Your TDEE adapts depending on intake (metabolic adaptation), and the body uses calories with varying efficiency.

Are all calories equal?

Mathematically yes (1 kcal = 1 kcal). Practically, no. Food quality changes how the body uses calories:

How to track your calories

Several methods, in order of accuracy:

1. Weighing + app (max accuracy)

Weigh every food, log it in MyFitnessPal/Yazio. Tedious at first, becomes automatic in 2-3 weeks.

2. Visual estimation (intermediate)

Hand-portion methods, picture references. Margin of error: ±15-25%.

3. Habit-based (long-term)

After tracking, you internalize portions and food values. The most sustainable level.

Common mistakes

Key takeaways

Calories are the foundation of every nutritional strategy. Calculate your TDEE, set a goal (deficit, maintenance, surplus), track for a few weeks until it becomes second nature. Don't ignore food quality, but never lose sight of the total. Energy balance + protein + training = body composition.