Jake Gyllenhall and model Alyssa Miller have decided to break up after six months of dating.

Jake Gyllenhaal, Alyssa Miller Split

Gyllenhaal’s busy filming schedule is thought to be largely to blame for the end of his relationship with Miller, 24. "Things were really good between Jake and Alyssa right up until he had to leave for L.A. to go shoot a movie [‘Nightcrawler’] in the fall," a source told Us Weekly. "Then the distance just really got to them."

For Nightcrawler, in which Gyllenhaal plays a hungry news reporter who’s uncovered the world of underground crime in Los Angeles, the actor dropped a significant amount of weight. While he’d been living in New York close to Miller in preparation for the role, he had to ship across the country to film the thriller.

Along with distance driving a wedge between the couple, Miller and Gyllenhaal are said to be looking for different things in a relationship. Miller may have been in it for the long haul, but Gyllenhaal, 33, isn’t ready to settle down just yet. "They were apart for the holidays, and things weren't good with them even before that," an insider told Us. "She's very much a long-term relationship girl. He's not as much of that mindset."

Gyllenhaal and Miller began dating in June after meeting at a gym they both belong to in New York. Miller is the latest in a long list of celebrity exes of the Prisoners actor, which includes Kristen Dunst, Reese Witherspoon and Taylor Swift.

– Chelsea Regan

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For More Jake Gyllenhaal News:

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Jake Gyllenhaal Steps Out With Model Girlfriend Alyssa Miller