How Calories Work - Complete Beginner's Guide
By: Yehia Yehia | May 30, 2025
What Is a Calorie?
A calorie is a unit of energy. In nutrition, it measures the energy food provides. One dietary calorie equals 1 kilocalorie (kcal), or 1,000 calories in physics. Your body needs calories to function, even at rest.
How Your Body Uses Calories
- Basal Metabolic Rate (BMR): Calories used for basic body functions like breathing and heartbeat.
- Physical Activity: Any movement or exercise burns calories.
- Thermic Effect of Food (TEF): Calories used to digest and process food.
Calorie Maintenance and TDEE
Your Total Daily Energy Expenditure (TDEE) is the number of calories you burn per day. It's based on your BMR, activity level, and digestion. Use an online TDEE calculator to estimate your maintenance level.
How to Lose Fat Using Calories
- Create a calorie deficit (eat fewer calories than you burn).
- A safe deficit is 300-500 kcal per day.
- Track food intake using apps like MyFitnessPal or Cronometer.
- Focus on high-volume, low-calorie foods: vegetables, lean protein, fruit.
How to Gain Muscle Using Calories
- Create a calorie surplus (eat more than you burn).
- A safe surplus is 250-400 kcal per day.
- Eat enough protein (1.6-2.2g per kg body weight).
- Train with resistance 3-6 times per week.
Common Calorie Myths
- "All calories are equal": Not true. 200 calories from candy vs. from chicken affect your body differently.
- "You must eat 6 small meals daily": Meal timing matters less than total calories.
- "Starving helps you lose weight faster": It slows metabolism and burns muscle.