You may notice that most food labels and diets refer to the “percent of daily values.” That percent is based on an average person eating 2000 calories per day. However, chances are you are not “average” and may need more or fewer calories than 2000 in order to maintain a healthy weight. Your needs are based on your height, weight, age, gender and level of physical activity.
There are several ways to determine how many calories you need:
- basal metabolic rate
- physical activity
- thermic effect of food
The Basal Metabolic Rate (BMR) is the amount of energy (calories) your body needs while resting. This accounts for about 60 to 70 percent of calories burned in a day. In general, men have a higher BMR than women. One of the most accurate methods of estimating your basal metabolic rate is the Harris-Benedict formula:
- Adult male: 66 + (6.3 x body weight in lbs.) + (12.9 x height in inches) – (6.8 x age in years) = BMR
- Adult female: 655 + (4.3 x weight in lbs.) + (4.7 x height in inches) – (4.7 x age in years) = BMR
To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows:
- If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
- If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
- If you are moderately active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
- If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725
- If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9
Total Calorie Needs Example
If you are sedentary, multiply your BMR (1745) by 1.2 = 2094. This is the total number of calories you need in order to maintain your current weight.
Calorie Needs to Lose Weight
There are approximately 3500 calories in a pound of stored body fat. If you subtract 3500 calories each week through diet, exercise or a combination of both, you will lose one pound of body weight. (On average 75% of this is fat, 25% lean tissue) If you create a 7000 calorie deficit you will lose two pounds and so on. The calorie deficit can be achieved either by calorie reduction alone, or by a combination of eating less and doing more. This combination of healthy eating and physical activity is best for achieving and maintianing a healthy weight.
If you want to lose fat, a useful guideline for lowering your calorie intake is to reduce your calories by at least 500, but not more than 1000 below your maintenance level. For people with only a small amount of weight to lose, 1000 calories is too much. As a guide, the American College of Sports Medicine (ACSM) recommends that calorie levels never drop below 1200 calories per day for women or 1800 calories per day for men. Even these calorie levels are quite low.
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Sources:
- http://health.howstuffworks.com/question457.htm
- http://www.bmi-calculator.net/bmr-calculator/bmr-formula.php
- http://www.bmi-calculator.net/bmr-calculator/harris-benedict-equation/
