Week #3: Do You Really Understand Calories?

You've heard about the word "calories" all the time. There are calories tracker apps on phones for your benefit. But do you know how the entire metabolism and breakdown of calories work within your body?

INTRODUCTORY VIDEO

Standard YouTube license: What is a Calories? uploaded by TED-Ed

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DISCUSSION

Since this video is not too Chemistry-based, the discussion is gonna be shorter than usual.

Calories, first of all, refer to the amount of energy each individual item of food stored in its chemical bonds (often of protein, carbohydrate, and fat molecules). When doing Chemistry homework, we calculate the energy of bonds broken and formed and determine whether it is an endothermic or exothermic reactions (and doing other exerices such as creating an energy diagrams), we often use the units of kJ or kJ/mol. Calories is just a different unit to refer to energy, especially in the context of food.

This concept is a simple example of the First Law of Thermodynamics. According to this, energy is neither burned nor destroyed. It transforms among different forms. When you eat a food, calories (in chemical energy) are "burned" and transformed into other useful forms such as kinetic energy (for your movements), heat energy (when you're sweat), sound energy, etc. If calories are not burned, it remains as chemical energy and store in your body. Unfortunately for us, the first-choice storage is fat, and that's why slow metabolic rate and lack of exercise, which hinder the burning of calories input, lead to obesity due to excessive fat¹.

Examples of Fiber Food

Because fiber food takes more energy to digest (as stated in the video), they are often used as a source of food for people who hope to lose weight. By this way, the energy used for digestion is higher than the usual 10% (so you burned more calories already). Fiber food are also believed to create a feeling of fullness, causing you not to over-eat².


Finally, this video ends in a very ironic way. Perhaps this is for us to remember. Nutrition labels are necessary to acknowledge the amount of calories the food itself contains. The amount of calories our bodies actually absorb is lower than this number, but how much lower depends on different factors that are not the same among individuals, so a food label should not the only decisive information.

Read but don't overestimate - Also these are some useful advices on how to read labels as well 

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Sources
Thumbnail background from FiveHourDiabetic
Calories image from That Sugar Film
Fiber Food from HealthDefine
Food Label from Mars Food
¹ Calories Explained
² The 150 Healthiest Foods on Earth [Book]