All foods contain calories, put simply, a calorie is a unit of energy.
So calories are the amount of energy we get from the food or drink we consume. We also use the term calories when we talk about the energy we expend carrying out daily activities [1].
All of our bodies’ use calories to perform essential body functions and activities throughout the day. Everything from breathing, thinking, walking, running, sleeping, talking and eating.
The number of calories we each need each day depends on our activity level and metabolic rate. This means that everyone is different and there is no one size fits all approach to determining how many calories we each need. Everyone’s daily calorie requirements will fluctuate daily, depending on our age, body composition, growth and activity level [2].
Energy is not only quantified by calories, but also kilojoules (kJ). Here in New Zealand food labels tend to display the latter. But, both being units of measure of energy, there is an equation to convert calories from kJ. Simply divide the kJ figure by 4.184, or 4.2 for simplicity’s sake (e.g. 1050 kJ / 4.184 = 251 calories)[2].
Calories can be useful to calculate and track how much energy we are consuming, but it is important to note that they do not tell us anything about the quality of the food we’re eating.
All calories when consumed by the human body are not equal [3]. This is because our body needs more than just calories, but nutrients too. For example, eating 100 calories from vegetables is going to give your body more nutrients than 100 calories of chocolate.
The term ‘empty calories’, refers to calories that provide energy but very little nutrients. Foods that are considered ‘empty calories’ still deliver that calories, which is predominantly from sugars or saturated fats. These tend to be highly processed foods. These foods provide very little dietary fibre, minerals, vitamins, amino acids or antioxidants [4]. Alcohol is also considered an empty calorie food item.
Bottom line, calories are important and we need the energy they provide to keep us alive and our bodies functioning well. It is best to focus on fueling our bodies with high quality, nutrient-rich foods. These are mostly plant foods, and are unprocessed or minimally processed.
[1] https://www.livescience.com/52802-what-is-a-calorie.html
[2] https://www.nhs.uk/live-well/healthy-weight/understanding-calories/
