What are calories and why do they matter?
A calorie is a unit of energy measurement. When we talk about food, we are actually referring to kilocalories (kcal) — the energy that food provides to the body and that is used to maintain all vital functions and perform physical activities.
Your body needs constant energy to function, even at rest. This energy comes from the three main macronutrients:
- Carbohydrates: 4 kcal per gram (preferred source of quick energy)
- Proteins: 4 kcal per gram (tissue building and repair)
- Fats: 9 kcal per gram (concentrated energy and hormonal functions)
The balance between the energy consumed (food) and the energy expended (metabolism + activities) determines whether you will maintain, lose, or gain weight. This is the basis of the first law of thermodynamics applied to nutrition.
Understanding TDEE: Components of energy expenditure
TDEE (Total Daily Energy Expenditure) is composed of four main elements:
BMR - Basal Metabolic Rate (60-75% of TDEE)
Energy spent to maintain vital functions at absolute rest: breathing, circulation, cell production, temperature regulation. It is the largest component of daily caloric expenditure in sedentary people.
EAT - Exercise Activity Thermogenesis (5-30% of TDEE)
Energy spent during structured exercises: weight training, running, swimming, cycling. Varies enormously between sedentary people (5%) and athletes (30%).
NEAT - Non-Exercise Activity Thermogenesis (15-30% of TDEE)
Energy spent in non-exercise activities: walking to work, climbing stairs, gesturing, standing, restlessness. People who are very active in their daily lives can burn 2000 kcal/day just with NEAT.
TEF - Thermic Effect of Food (8-15% of TDEE)
Energy spent to digest, absorb, and process food. Proteins have a high TEF (20-30%), carbohydrates medium (5-10%), and fats low (0-3%). Therefore, diets rich in protein slightly increase metabolism.
How to calculate your TDEE: Detailed step by step
Step 1: Calculate your BMR (Basal Metabolic Rate)
We use the Mifflin-St Jeor formula, the most accurate for the modern population:
Women: BMR = (10 × weight) + (6.25 × height) - (5 × age) - 161
Example: Man, 30 years old, 80kg, 175cm BMR = (10 × 80) + (6.25 × 175) - (5 × 30) + 5 = 1,749 kcal/day
Step 2: Apply the physical activity multiplier
Multiply your BMR by the factor that best describes your routine:
- 1.2 - Sedentary: Office work, no exercise, little movement
- 1.375 - Lightly active: Daily walks + 1-3 light workouts/week
- 1.55 - Moderately active: 3-5 intense workouts/week
- 1.725 - Very active: 6-7 intense workouts/week or physical work
- 1.9 - Extremely active: Athletes with 2x/day workouts + physical work
Continuing the example: Moderately active man (3-5 workouts/week) TDEE = 1,749 × 1.55 = 2,711 kcal/day
Step 3: Adjust according to your goal
🎯 Maintain weight
Consume exactly your TDEE (2,711 kcal in the example). Monitor weight weekly and adjust ±100 kcal if necessary.
📉 Lose weight (deficit 15-25%)
Moderate deficit: 2,711 × 0.80 = 2,169 kcal/day (loss of ~0.5kg/week)
Aggressive deficit: 2,711 × 0.75 = 2,033 kcal/day (loss of ~1kg/week)
📈 Gain muscle mass (surplus 10-20%)
Moderate surplus: 2,711 × 1.10 = 2,982 kcal/day (lean gain)
Aggressive surplus: 2,711 × 1.20 = 3,253 kcal/day (rapid gain + fat)
Practical strategies for calorie control
For those who want to lose weight
- Prioritize protein: 1.6-2.2g/kg of body weight preserves muscle mass in a deficit
- Volumize meals: Fiber-rich vegetables increase satiety with few calories
- Scheduled meals: 3-5 meals/day avoids extreme hunger and cravings
- Hydration: 35ml/kg of body weight; thirst can be confused with hunger
- Adequate sleep: 7-9h/night optimizes satiety hormones (leptin and ghrelin)
- Progressive deficit: Start with a 15% deficit and adjust according to results
- Strategic refeeds: 1 day/week at TDEE helps metabolism and adherence
For those who want to gain muscle
- Moderate surplus: Gains of 2-4kg/month minimize fat accumulation
- Strength training: 3-6x/week with load progression is essential
- Sufficient protein: 1.8-2.4g/kg optimizes muscle protein synthesis
- Carbohydrates around training: Maximizes performance and recovery
- Frequent meals: 4-6 meals/day makes it easier to reach a high caloric volume
- Calorie-dense foods: Peanut butter, olive oil, nuts add calories without volume
- Monitor body composition: Gain of more than 0.5% BF/month indicates excessive surplus
Apps and tools for calorie tracking
📱 MyFitnessPal
Largest food database (14+ million). Barcode scanner, automatic macro calculation, integration with exercise apps.
📱 FatSecret
Free and complete. Simple interface, food diary, food photo recognition, active community.
📱 Cronometer
Focus on micronutrients. Ideal for those seeking complete nutritional optimization, not just calories and macros.
📱 Lose It!
Gamified interface. Challenges, badges, engaged community. Good for those who need extra motivation.
Common errors in calorie control
❌ Underestimating actual consumption
Studies show that people underestimate consumption by 30-50%. Use a digital scale for portions in the first few months. Forgotten oils, sauces, and snacks add up to hundreds of calories.
❌ Very aggressive deficits
Deficits above 30% (750+ kcal/day) cause loss of muscle mass, metabolic slowdown, fatigue, and risk of binge eating. Healthy weight loss is a marathon, not a sprint.
⚠️ Ignoring metabolic adaptations
After 8-12 weeks in a deficit, the body adapts and reduces NEAT, TEF, and even BMR. Take "diet breaks" of 7-14 days at TDEE every 2-3 months of deficit.
⚠️ Confusing weight on the scale with real progress
Weight fluctuates 1-2kg daily due to water, glycogen, and intestinal content. Use weekly averages and measure circumferences (waist, hips, arms) to assess real progress.
When to adjust your calories
Your TDEE is not fixed. Adjust your calories when:
- Weight plateau (3+ weeks): Reduce 100-200 kcal or increase NEAT
- Loss of more than 1% of body weight/week: Excessive deficit, increase 100-200 kcal
- Chronic fatigue or performance decline: May indicate a very aggressive deficit
- Significant weight change (±5kg): Recalculate TDEE with new weight
- Change in exercise routine: New activity level changes multiplier
- Signs of overtraining: Insomnia, irritability, frequent injuries require caloric increase