Your daily calorie requirements vary depending on your age, gender, weight and activity level. In general, eating more calories than your body needs leads to weight gain; eating fewer, weight loss. Nutrition guidelines give rough estimates of how many calories you need, but you can get precise with a simple mathematical formula.
Significance
All foods and beverages contain calories, which, in scientific terms, are units of energy. Though the nutritional quality and makeup of foods varies, a calorie in a slice of frosted chocolate cake is the same as a calorie in an apple. Each provides energy for the body, which constantly requires energy, even at rest.
Here's the difference between the calories in the apple, and the calories in the cake. The fruit is more nutritious in terms of containing vitamins and fiber and not containing saturated fats. The apple also contain far fewer calories per serving (95 for a 3-inch medium apple) than the cake, (235 for 1/8 of an 18-oz. cake.) That means, if you're eating 2,000 calories per day, you can eat more apples than you can slices of chocolate cake.
Adult Guidelines
In general, the more active you are, the more calories your body needs. Most women require fewer calories than men. In addition, daily calorie requirements drop as we age.
The American Heart Association gives these guidelines for adults:
--Women age 19 to 30 require 2,000 calories daily if sedentary, 2,400 if active.
--Women age 31 to 50 require 1,800 calories if sedentary, 2,200 if active.
--Women age 51-plus require 1,600 calories if sedentary, up to 2,200 if active.
--Men age 19 to 30 require 2,400 calories if sedentary, 3,000 if active.
--Men age 31 to 50 require 2,200 calories if sedentary, up to 3,000 if active.
--Men age 51-plus require 2,000 calories if sedentary, up to 2,800 if active.
For women who are pregnant or breast-feeding and anyone with a metabolic disease such as diabetes, online calculators may overestimate or underestimate your needs. Consult your health practitioner.
Pediatric Guidelines
The American Academy of Pediatrics gives these daily calorie guidelines, based on sedentary lifestyles. Active children require more calories:
--Girls age 4 to 8 require 1,200 calories.
--Girls age 9 to 13 require 1,600 calories.
--Girls age 14 to 18 require 1,800 calories.
--Boys age 4 to 8 require 1,400 calories.
--Boys age 9 to 13 require 1,800 calories.
--Boys age 14 to 18 require 2,200 calories.
Formula
To calculate your daily calorie needs, you need to know your basal metabolic rate or BMR. Here's how:
The BMR formula for women is 655 + (multiply 4.35 by weight in pounds) + (multiply 4.7 by height in inches) - (multiply 4.7 by age in years)
The BMR formula for men is 66 + (multiply 6.23 by weight in pounds) + (multiply 12.7 by height in inches) - (multiply 6.8 by age in years)
Once you have your BMR number, honestly assess your activity level to determine your total daily calorie needs:
--If you do little or no exercise, multiply your BMR by 1.2.
--If you are lightly active one to three days a week, multiply your BMR by 1.375.
--If you do moderate exercise or sports three to five days a week, multiply your BMR by 1.55.
--If you exercise hard six to seven days a week, multiply your BMR by 1.725.
--If you are extra-active, with a demanding physical job and hard exercise, multiply your BMR by 1.9.
As you lose weight or gain weight, or get older, your BMR will change, so just recalculate.
Losing Weight
A pound of body fat is equal to 3,500 calories. If you're trying to lose weight, you can drop a pound a week by creating a deficit of 500 calories per day. Over seven days, that's 3,500 calories. To cut 500 calories, eat 250 fewer calories and burn 250 more calories through exercise each day.
On food labels, calories are listed at the top of the "Nutrition Facts" box. Pay attention to the "serving size" and "servings per container" that are also listed. A bag of Doritos, for instance, says it contains 150 calories per serving. Guess how many servings are in the bag: about 14. Eat the whole bag, and you consume 2,100 calories.
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