What is a Calorie?
Updated: May 13, 2020
Nicolas Clément, a French chemist and physicist, first defined the calorie as a unit of heat or thermal energy in 1824. The word "calorie" comes from the Latin word calor, which means "heat."
Not having enough calories in your diet can have negative effects on you, from losing muscle mass, finding it difficult to concentrate and not having sufficient energy to carry out day to day things. This is because we need energy to function, our brains, our muscles and the cells in our body, without them our bodies will "stall" and likely crash.
There are three types of food nutrients that deliver caloric energy, these are fats, proteins, and carbohydrates:
1g of Protein contains 4kcal
1g of Carbohydrate contains 4kcal
1g of Fat contains 9kcal
The human body is designed to run highly effectively on Carbohydrates, it can run on Proteins and Fats but much less effective, this is because Carbs contain molecules of glucose that can be easily broken down by the body to be broken down into individual units of energy, Protein and Fats need to be converted into glucose making them less efficient.
Protein and Fats do have other more important uses though. Protein is important for helping to build muscle and antibodies to protect you agains illness, whilst Fat is essential for helping the body absorb vitamins and reduce the risk of heart disease.
Back to Calories.
How many calories a person needs each day totally depends on the individual’s activity level and resting metabolic rate, this can vary hugely from person to person, that's why you should never consume the same amount of calories as someone else and expect the same outcome.
When you consume calories the body breaks down these nutrients with enzymes in the mouth, stomach and intestines, this process turns fats into fatty acids, sugar into simple sugars and proteins into amino acids. The body then uses oxygen cells throughout the body to convert to energy, this process is called Metabolism.
The majority of calories we burn each and every day are used just to keep our body running with about half used to power organs such as the brain, liver, kidneys, and heart. We use the rest of the calories for physical activity and the process of converting food to energy. Calories not used by the body is then stored, first in the liver and eventually as fat cells. This is why people that overeat calories put on weight and body fat over time.
Guidelines suggest that the average adult woman needs to consume about 2,000 calories a day, and the average adult man about 2,500, but these are just an estimate. How much energy your body needs varies based on many factors, including activity level, age, height and more.
Eat more calories than you need and body will convert that unused energy into muscle, short term or fat tissues, long term and if you aren’t able to eat enough calories, your body will tap into those stores to fuel itself. This is why it is possible for severely overweight and obese people to have lower calorific intake than normal.
Calorie Deficit and Calorie Surplus are terms used to describe a person being in a Negative Energy Balance (less calories than your body burns) and a Positive Energy Balance (more calories than your body burns). There are two things that are certain with both of these, if you are in a caloric deficit you WILL lose fat (and weight) and if you are in a caloric surplus you WILL gain fat (and weight). The laws of thermodynamics can not be changed.
If you are trying to lose fat and weight but aren't then you ARE NOT IN A CALORIE DEFICIT.
It's that simple. You are either miscalculating your calories and are still in a SURPLUS, or your physical output (calorie burn) is likely not at the level you need it to be or think its at.
Overall calories are complex, but once you grasp these basic principles, reaching your goals should be that bit easier.