The minimum amount of calories you need per day depends on your age, gender, height and physical activity level. Your body requires a certain amount of calories (kilocalories) to function, for example, circulating blood, growing and repairing cells, and breathing. If you incorporate an exercise program, increase your calorie intake, since your activity level will also be increased. When too little calories are consumed your body's metabolism can become slow, as a result weight loss becomes harder to achieve.
Metabolism
Your body's metabolism is the natural process in which it converts calories into energy. Originating from the word kilocalorie, a calorie is used to characterize the energy-producing potential in food. Calories are combined with oxygen to release energy into your system and carry out everyday functions.
Basal Metabolic Rate
Basal Metabolic Rate (BMR) is the number of calories your body utilizes to function at rest. This activity is performed by your heart, brain, lungs, and other cells. Most cells in your body are found in the muscles, meaning the more muscle mass you have, the more calories your body needs to function.
Factors
There are factors that determine your basal metabolic rate; age, gender, body composition, and activity level. As you age, your body loses muscle mass and slows down calorie burning. Men tend to have less body fat than women, thus burn more calories at rest. A person with a higher body fat percentage will burn less calories rather than someone with a lower percentage.
BMR can change greatly depending how much activity you do each day. A sedentary lifestyle leads to a lower BMR and a highly active person will have a higher BMR. A sedentary lifestyle consists of no or very little physical activity, while a highly active lifestyle consists of daily manual labor along with three to five days of exercise.
How To Determine
A formula, Harris-Benedict Equation, is used to determine the minimum amount of calories you need in a day. It is more accurate than estimating your total calorie needs based only on your body weight. The Harris-Benedict Equation is the most widely used formula for BMR; however it does not take into consideration lean body mass. If you are very muscular or obese, this may not work for you. There are two different formulas depending on gender.
For men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)
For women: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)
For example, a 20-year-old woman who weighs 120lbs (54.5 kg) and is 5'6" tall (167.6cm). Her BMR = 655 + 523 + 302 - 141 = 1339 calories/day
Concerns
If you consistently consume too little calories on a daily basis, it can become detrimental to your body. When this happens your body compensates by decelerating natural processes and holding onto stored fat for survival. Meaning, your metabolism will slow down and make it more difficult to lose body fat. This is the opposite of what you want if you are beginning a weight loss program.
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