228,000 calories per day

The “calorie” is an interesting unit of measure. We often think of it in terms of nutrition (“this cookie is 200 calories”), which isn’t wrong, but it’s really a unit of energy. It’s officially described as:

The large calorie, food calorie, dietary calorie, or kilogram calorie is defined as the amount of heat needed to raise the temperature of one kilogram of water by one degree Celsius.

So we think of it as food, but it’s really energy. In our case, the food provides us energy, but we can calculate calorie usage for all other kinds of energy use. Stephen Fry’s “ Great Leap Years “ podcast series explained much of the world in terms of calorie consumption, and it’s a series I’ve listened to a few times.

In his book Homo Deus, author Yuval Noah Harari explains how our calorie usage has grown to over 228,000 calories per day; 2,000 for us to eat, and the rest for us to use. From his book:

In the Stone Age, the average human had at his or her disposal about 4,000 calories of energy per day. This included not only food, but also the energy invested in preparing tools, clothing, art and campfires. Today Americans use on average 228,000 calories of energy per person per day, to feed not only their stomachs but also their cars, computers, refrigerators and televisions. The average American thus uses sixty times more energy than the…