Zero sum doesn’t mean there is a loser to every transaction. It just means that the net total change is zero. You buy a friend a beer, and you get a beers worth of camaraderie.
When you eat food, something had to die for that. It was a transfer of biochemical energy from that creature to you.
Even if it was a vegetarian meal, it got transported to you and dumped CO2 into the atmosphere. The truck probably hit bugs and maybe ran over some small wildlife.
If you didn't exist, there would be slightly less demand. If 300 million of you didn't exist, there would be a whole lot less demand. The world would be noticeably different.
Everything is energy expenditure and reallocation. Even hugging your son expends ATP that could have been used elsewhere. Hug him a million times and you will be very tired.
I'm not arguing that you shouldn't love your son. I'm saying that the world, at the most fundamental level, revolves around the availability of energy and resources. All of these things in the micro add up in the macro. And even if you aren't concerned about it, your government likely is.
Every single choice has some quantum of opportunity cost and will play out in butterfly effect fashion.
In terms of the energy you want to consume in a form factor you can utilize - food, coal if you want electricity today, plastics in tour phone, Amazon shipping, etc. - it's very much not constant.
