What Is a Calorie—and How Many Do You Need?

What It Is

A calorie is a measurement of energy that is taken into the body through food and drink. It’s then used (or “burned”) through physical activity. Simply put, a calorie refers to one of these energy units.

As the Journal of Nutrition points out, the way a calorie is defined has fluctuated over time. The calorie was originally defined in 1863 as “the heat needed to raise the temperature of 1 kg of water from 0 to 1°C.” By the 20th century, this definition had been updated to refer to 4.18 joules. Since we rarely think in such terms or increments, a calorie calculator, which suggests daily caloric intake based on height, weight, age, and activity level, is one of the simpler, more effective ways to understand the number of calories your body needs.

Finding Balance

The key to proper caloric intake is achieving a balance between the number of calories you consume and the number of calories you burn. When you take in more calories than you expend through physical activity, the excess calories wind up being stored in the body as fat. When you have a deficit of calories compared to the amount of energy needed for physical activity, this is when weight loss occurs. For those who appreciate visual aids, this short video from TED should do the trick.

Because caloric intake has such an obvious and profound effect on fat stores, it’s often identified as a major target area for those hoping to lose weight. Exercise, however, is a crucial component too. As Michele Olson, a professor of physical education and exercise science at Auburn University, notes in an interview with the Huffington Post, “You can lose weight with diet alone, but exercise is an important component. Without it, only a portion of your weight loss is from fat.” As is true of other components of nutrition, the quality of calories matters and balance is crucial.

Up next, keep reading to learn why cutting calories could be sabotaging your health goals.