Doing something "in moderation" means not doing it excessively. For instance, someone who moderates their food consumption tries to eat all food groups, but limits their intake of those that may cause deleterious effects to harmless levels.
One who holds or champions moderate views or opinions, especially in politics or religion. 1. To cause to be less extreme, intense, or violent. 2. To preside over: She was chosen to moderate the convention. 1. To become less extreme, intense, or violent; abate. 2. To act as a moderator.