In general, people associate working hard with making money (wealth). Seems reasonable. Work hard, or more hours, build your wealth. Work less, or not at all, and less wealth you will have.
But, as it's easy to see in this case, your bank account is not defined by how hard or how much you WORK. It is defined by how many DOLLARS you have. There are lots of folks who work plenty hard for long hours but are not capable of building much wealth. One obvious reason for this is that some people get paid peanuts. Put another way, monetary wealth is about how much MONEY you have, and working is a only a relative measure of money. I know plenty of people (hi Aspen) that don't work hard, or much, but have plenty of money. Let me now show you how this situation applies to calories and health.
Most people associate calories in/calories out with health (and weight loss). Again, seems reasonable. More calories in than out, health goes down and weight goes up.
BUT, your body does not deal in calories. It's currency is nutrients. The reading on a bomb calorimeter when someone flips the swith and literally incinerates an apple is NOT a measure of it's nutrient value. Your body utilizes the nutrients in food, or it's metabolites, for everything from fuel, to storage, to repair and regeneration. NUTRIENTS are used to build your health in the same as money builds your wealth.
Here is the simple analogy: Your bank account is only correlated with how hard and how much you work. The bottom line is how much money you put into it. Similarly, your health is only correlated with the calories in the food you ingest. The bottom line is how many nutrients you eat.
While it's easy to fix the above wealth example by merely talking about how much money you make and spend instead of how much you work, things get WAY more complicated when you want to start taking about health in terms of nutrients and exercise. For example, how many nutrients are actually in food (seasonal/ regional/ soil differences)? How many of them do you absorb, or don't absorb (and why)? What nutrients do our gut bacteria feast on and then in return make for us to use? And on and on.
I'm not fond of talking about calories in terms of health and nutrition, but a) it's a rough gauge of food density which is here to stay, and b) there is no simple way to replace it in broad spectrum terms. Too much variability.
So where does that leave one in terms of what to think about calories? That is for you to decide grasshopper.