How to decrease troops consumption?

There are a few ways:

Become a Trader: Traders get 50%less troop consumption, but there are downsides to this class as well

Dismiss Troops: Let troops get wounded and dismiss them in the hospital to reduce troop numbers.

Use Heroes: Development Heroes that can be stationed in the Troop training buildings (fighter, vehicle, shooter training camps) have Skills that reduce food / fuel upkeep. Recruit these heroes and unlock the skill. Orange heroes are Drill Master for fighters, The mechanic for vehicles and Master Marksman for shooters.