Different people need different amounts of calories to maintain a healthy weight. Calories help fuel the body and prevent it from burning stored fat for basic functions. When you eat the proper amount of calories, your body functions efficiently and you neither lose nor gain weight.
Basal Metabolic Rate
Your basal metabolic rate indicates how many calories your body needs to perform basic functions like breathing and digestions. Women can calculate BMR by multiplying your weight in pounds by 4.35, then adding 655. Add that number to the product of 4.7 multiplied by your height in inches. Then multiply 4.7 by your age in years and subtract that number from your previous total.
For men, calculate your BMR by adding 66 to the product of 6.23 multiplied by your weight in pounds. Add that to the product of 12.7 multiplied by your height in inches. Finally, multiply 6.8 by your age in years and subtract that number from your previous total.
Activity Level Affects Caloric Requirements
The Harris-Benedict equation calculates the total number of calories you need by taking your basal metabolic rate (BMR) and multiplying it by an activity factor. There are five activity levels; the more active you are, the higher the multiplier is to calculate the number of calories to maintain weight.
If you are a 5-foot-4-inch, 30-year-old female weighing 140 pounds, you need 1423.8 calories daily to maintain basal metabolic function. If you are lightly active, multiply that number by 1.375; if you are moderately active, multiply it by 1.55. You would need about 2,207 calories to maintain your weight of 140 pounds if you are moderately active. If you are taller, more active or male, you will need more calories.