I hate this reference in the article that I hear as a "truism" over and over again as if it is some sort of litany against folks who are simpy hungry. Why are we hungry?

In part because of the load of food we eat that is not nutritionally complete nor naturally designed for our bodies, but we eat an awful lot on the basis of advertising.

In part because we are under a lot of stress in our urban lifestyles and food is comforting psychologically and physically.

In part because we are not active enough and fill time that we would be doing activities eating instead, but it doesn't satisfy us, so we are fixed with chronic munchies.

In part because food in the USA is relatively cheap and plentiful (but it's usually not the stuff that is good for us).

I will repeat my analysis again.

People talk as if a "calorie" exists in a vacuum (which it does not). Water will boil at different temperatures under different atmospheric pressures, meaning that more or less calories may be used for the same activity dependent on additional factors.

Metabolism is dependent on at the very least:

1) what type of food you eat (100 calories of candy vs. a piece of cheese have completely different effects on the body)
2) your activity level
3) your genetic code (why are some people who eat exactly the same things diabetic while others are not? why are some people built tall and thin and others short and wide?)

I'm sure there are a lot more factors involved.

That we as a society are getting heavier and less healthy is true, but I think that the single most powerful factor is a lack of physical activity, followed by an excess consumption of food which is not what our bodies are designed to take in, particularly high-carb processed foods, particularly sugar, particularly soda (which folks have come to expect as being a normal accompaniment of a meal).