Difference Between Calories and Energy

In order to survive and do our day to day work, we need to obtain energy in various ways. Usually, all the animals obtain energy from their diet, and they oxidize their food to obtain energy. In a biological system, the energy is described in terms of Calories. Therefore, the key difference between calories and energy is that Calorie is a unit of energy. In this article, Calories, energy, and the difference between are described in more detail.

What is Calorie?

Calorie is a unit used to measure the amount of energy in a particular food. The energy denoted by a calorie is equal to the amount of energy needed to increase the temperature of 1 mL of water by one degree Celsius. Nutritionists usually talk about large amounts of calories, and hence, it is more useful to consider kilocalories. However, in food science, kilocalorie is also called a Calorie abbreviating as ‘kcal’ or ‘Cal’.

The caloric energy of a particular food can be measured by bomb calorimeter in which the amount of heat released is measured and recorded by incineration of the food. The caloric value of a food varies with the number and type of chemical bonds between atoms. For example, one gram of sucrose contains 4 Calories, but one gram of glucose contains 3.7 Calories. Enzymes and coenzymes (biochemical catalysts) are responsible for the conversion of Calories into fuel that can be used by cells.

What is Energy?

There are no better definitions for energy, but simply it can be defined as the capacity to do work. According to the laws of thermodynamics, there are some basic principles we should consider when talking about energy. One is that the energy cannot be created or destroyed, but it can be converted from one form to another. Animals gain energy by oxidizing the food they eat. Plants, however, can independently produce their own energy by photosynthesis.

Energy is in various forms, such as kinetic energy, potential energy, thermal or heat energy, electrical energy, chemical energy, etc. Usually, energy is measured in kilojoules. However, the energy in biological systems is often measured in terms of Calories (4.184 kilojoules = 1 Calorie).

What is the difference between Calories and Energy?

Definition of Calories and Energy

Calorie: Calorie is a unit of energy used by nutritionists to measure the amount of energy in a particular food.

Energy: Energy is the capacity to perform a work by utilizing the physical or chemical resource.

Unit of Measurement

Calorie: In biological systems, energy is measured in Calories, which is abbreviated as ‘kcal’ or ‘Cal.’

Energy: Usually, energy is measured in kilojoules, which is abbreviated as ‘kJ.’

Conversion – kJ to kcal

4.184 kilojoules = 1 Calorie or kcal


Image Courtesy:
1. \"Oxygen Bomb Calorimeter\" by Fz2012 (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons