Why are [airline meal](https://en.wikipedia.org/wiki/Airline_meal) portions so small, even on long-haul flights ?  
Sometimes it's not even enough for children, let alone adults.

I have some assumptions, but I would like to submit this question to those who are in a position to know the genuine reason(s).

[![img][1]][1]  
*(generic photo for illustration purposes only)*

Hungry passengers might choose another airline next time, so I don't think it's a winning marketing strategy.

Some answers say that larger meals are not necessary, because passengers don't burn a lot of calories while sitting. The point is entirely moot. People get hungry when their body gets less to eat than it is used to. The amount of burned calories on a single day is not what causes hunger. Much to the contrary – after doing lots of sport, I'm tired. Not hungry at all.

  [1]: https://i.sstatic.net/AwJ7n.jpg