What Exactly Are Calories, Anyway?
What we refer to in America as a “calorie” is actually a kilocalorie, or 1,000 calories. The calorie unit of measurement was invented by Nicolas Clement in 1824. The word calorie comes from the Latin “calor”, meaning “heat”, which is an apt description as calories really are units of heat energy.
A true calorie is defined as the amount of energy required to raise the temperature of one gram of water by one degree Celsius. Therefore, a kilocalorie is the amount of energy needed to raise the temperate of one kilogram of water by one degree Celsius. One kilogram of water is the equivalent of about one liter.
Your body gets calories through nutrients, including carbohydrates, protein, and fat. When your body burns calories, most of them actually exit through respiration; in other words, you breathe them out. You burn calories no matter what you’re doing, be it running, standing, sitting, or sleeping.
You Burn Calories Even in Your Sleep
Your body is constantly burning calories, and during sleep is no exception. During sleep, although you may think your body is at rest, there are actually many processes taking place. Calories are burned during sleep due to breathing, circulation, cell growth, nerve function, tissue repair, controlling body temperature, and many other processes.
So, exactly how many calories do you burn every night? This is dependent on many factors, such as age, height, weight, and muscle mass.
The rate at which you burn calories during sleep is quite similar to your basal metabolic rate. Your basal metabolic rate is how many calories you would burn in 24 hours if you were doing absolutely nothing the whole time. The majority of the calories you burn in a day go toward your basal metabolic rate.
Younger have higher basal metabolic rates than older people, and taller people have higher basal metabolic rates than shorter people. Fatter people have higher basal metabolic rates than thinner people, and those with more muscle mass have higher basal metabolic rates than those who aren’t as fit. There is a lot of variation in caloric expenditure between different people, so the oft-touted 2,000-kilocalorie daily diet in reality is not a one-size-fits-all affair.
Using Calorie Knowledge to Your Advantage
There are many calculators online to determine your basal metabolic rate. Once you have this number, you can figure out how many calories you need to eat daily to maintain your weight using the Harris-Benedict equations. These equations were developed in 1918, but have been revised since then to become more accurate.
There are approximately 3,500 calories per pound of fat. Therefore, to lose one pound of fat, you need to consume 3,500 fewer calories than you burn. You can eat 500 calories less than your daily caloric need to lose weight at a rate of one pound per week, or 1000 calories less to lose weight at a rate of two pounds per week.