Many factors affect your balance of resources, like:

- Your base is being attacked, and your resources are looted.
- Using resources in upgrading and building.
- Using resources for alliance donations
- Using resources to do research.
- Using resources to heal damaged units in the service center.
And many other things.

Note: Troops have a cost of living, and they consume food. If you want to know the total food used by your troops, click on your strength balance. You will find this information at the bottom of the screen (Troop Count - total marching troops - total food consumption - injury Count).