How Many Calories Am I Supposed to Eat a Day? Step-by-Step Guide

What Are Calories?

Calories are units of energy. When we eat and drink, we consume calories, which our bodies use as fuel for all activities, from breathing and thinking to exercising and working. The amount of calories you need each day depends on various factors, including your basal metabolic rate (BMR) and your level of physical activity.

Determining Your Caloric Needs

Basal Metabolic Rate (BMR)

Your BMR is the number of calories your body needs to maintain basic physiological functions like breathing, circulation, & cell production while at rest. Several formulas can calculate BMR, with the Harris-Benedict Equation being one of the most commonly used.

Harris-Benedict Equation

1. For Men: BMR=88.362+(13.397×weight in kg)+(4.799×height in cm)−(5.677×age in years)
2. For Women: BMR=447.593+(9.247×weight in kg)+(3.098×height in cm)−(4.330×age in years)

Total Daily Energy Expenditure (TDEE)

Once you have calculated your BMR, the next step is to determine your Total Daily Energy Expenditure (TDEE). TDEE represents the total number of calories you burn in a day, accounting for both your BMR and your physical activity level.

Activity Multipliers

• Sedentary (little or no exercise): BMR × 1.2
• Lightly active (light exercise/sports 1-3 days/week): BMR × 1.375
• Moderately active (moderate exercise/sports 3-5 days/week): BMR × 1.55
• Very active (strong exercise/sports 6 to 7 days a week): BMR × 1.725
• Super active (very hard exercise, physical job, or training twice a day): BMR × 1.9

By multiplying your BMR by the appropriate activity factor, you can estimate the number of calories you need to maintain your current weight.

Example Calculation

Let’s calculate the caloric needs for a 30-year-old woman who weighs 70 kg, is 165 cm tall, and is moderately active.

1. Calculate BMR:
   BMR=447.593+(9.247×70)+(3.098×165)−(4.330×30)
   BMR=447.593+647.29+511.17−129.9
   BMR≈1476.153
2. Determine TDEE (moderately active):
   TDEE=BMR×1.55
   TDEE=1476.153×1.55
   TDEE≈2287.038

So, this woman needs approximately 2287 calories per day to maintain her current weight.

Adjusting Caloric Intake for Weight Goals