If you are exercising for weight loss, it’s useful to understand the concept of a calorie deficit. In technical terms, a calorie is a unit of energy equivalent to the heat energy needed to raise the temperature of 1 gram of water by 1°C.
But more commonly, we use calories to measure the energy content and nutritional value of foods.Our bodies need calories to perform basic functions and allow us to engage in physical activity. When we are sick, our bodies need extra calories to fuel our immune systems.