How can I reduce troop consumption?

Troop consumption can't be reduced easily. One way is to be a Trader class, then one of the benefits is a 30% reduction in troop food consumption. There are downside to this as well though. Check the guide for Class details.

If you do not need all the troops then there are ways to remove some. See the guide here:

https://www.appgamer.com/last-shelter-survival/strategy-guide/how-do-i-reduce-my-troops