monomania

Example:He became a monomaniac about weight loss and cut himself off from all social events.

Definition:A person affected by monomania, someone who is obsessively dedicated to a single idea, often to an unhealthy degree.

Example:She was monomanically focused on winning the tennis championship and nothing else mattered to her.

Definition:In a manner characteristic of monomania, obsessed with a single idea or topic to the exclusion of all else.

Example:The town mayor's monomanical obsession with winning elections has blinded him to the real needs of the community.

Definition:A fixed, often overly intense preoccupation with a particular idea, which can be irrational or neurotic.