Everyone knows what you mean when you say you're going to see a Michael Bay movie. Very few directors get to become adjectives, but Bay, who's filming the fourth installment of the "Transformers" mega-franchise in Detroit this spring, has a name that is synonymous with huge special effects-driven extravaganzas for mass audiences.

So how come Bay's latest effort, the darkly comic "Pain & Gain" is so, well, unBay-like? The way he describes it, he was ready for a change. About 12 years ago, he read about the real-life Miami crime spree that's the basis for the darkly comic movie. But it was put on the shelf while he was busy with those robots-from-space mega-hits.

"It was that cool project that kind of sat there and I had wanted to do. The studios wanted me to keep doing these blockbuster-type movies," says Bay, whose "Transformers" franchise has earned more than $2 billion in global box office revenue.

After filming the third "Transform-ers" installment, he says, "I'm thinking, you know what, I'm going to make this little movie. 'Why do you want to do that?' Because there's an interesting movie in here and it's going to be fun."

It's interesting, all right, and not just because it's a chance to watch Bay venture into edgy, funny, disturbing territory usually occupied by filmmakers such as Quentin Tarantino and the Coen brothers. "Pain & Gain" stars Mark Wahlberg, Dwayne Johnson and Anthony Mackie in the bizarre story of three bodybuilders who have some deeply warped ideas about how to achieve and live the American dream.

The movie begins with Wahlberg's character, an ambitious gym trainer, reciting some typical bromides about hard work leading to success. But it becomes clear his glutes are bigger than his smarts or his scruples. Through kidnapping and extortion, he sets out to acquire the money and social position he thinks he deserves.

Wahlberg's bumbling accomplices are an ex-con who's found religion and rehab (Johnson) and a steroid-loving gym junkie (Mackie). Together, they target one of Wahlberg's rich clients (the marvelous Tony Shalhoub), and their crimes descend into gruesome territory.

The script by the writing team of Christopher Markus and Stephen McFeely ("Captain America: The First Avenger") is inspired by Miami New Times articles by Pete Collins that covered the stranger-than-fiction 1990s saga of the notorious Sun Gym gang. The characters played by Wahlberg and Mackie are on death row for two murders. Johnson's character is a fictional composite. The cast also includes Ed Harris as a detective who tracks the gang and Rebel Wilson as a woman who falls for Mackie's character.

The bizarre story made a big impression on Bay, who was drawn in by the idea of characters looking for the American dream in all the wrong ways.

"It was something that I just had a style in my head - right when I read the articles - of how I wanted to shoot a movie like this," he recalls. "It's not your normal movie. It's a wild ride. You go into the criminals' minds and sometimes you sympathize with them and you see their psychoses."

Some involved with the real case have expressed concerns the movie will trivialize the brutal nature of what happened. But the makers of the film have been clear they're not out to make the perpetrators of the crimes sympathetic or play down the horrible things they did. The movie's focus is the mind-set of the criminals.

"It's showing all these gray areas of criminals where they think they're better than other people. They think they can have a wonderful, loving wedding and the very next day they can have a guy tied up in a factory or warehouse and try to extort him. It's a bizarre lifestyle."

Bay had talked to Johnson about eight years ago about doing the movie. He'd been looking for a while for a project to work on with Wahlberg - the actor the screenwriters had in mind for the lead while they were creating the script. Wahlberg wound up putting on 40 pounds of muscle for the role.

Recalls Bay, "Mark just said, 'I grew up in the gym. I know this guy. I've been a convicted felon, I've gone to prison. Mike, I know these type of guys.'"

Bay says he wanted the audience to be conflicted about the characters, pointing out that Wahlberg's character, in the midst of his horrible activities, forms a neighborhood watch at one point. "There's a sweet side to this guy, but he's so bad. That's what I was really trying to show. There's different levels to life, and darkness sometimes lurks in real places."

The movie also delves into some social commentary about superficial interpretations of the American dream. In the gym world inhabited by Wahlberg and Mackie's characters, Bay says, "It's like, if my body were a little bit more shredded, I'd be a happier guy. If my biceps were a little bit bigger, I'd be happier. They're just never happy with what they've got."

Besides the intriguing subject matter, another lure for Bay was the opportunity to make a film with a scaled-back budget. Like a tycoon who can afford the finest restaurants but sometimes craves a fast-food burger, Bay seems to have enjoyed the challenge of getting the "maximum bang for a low budget." One handy economy measure? He was able to use his own dazzling home on Miami Beach as a location.

Next up for Bay is "Transformers 4," which he says isn't a reboot, but will take the franchise into a new direction with new stars, including Wahlberg. He sounds like "Pain & Gain" is just the sort of thing he needed to recharge his batteries before this next task.

"There's no harm, no foul when you're doing a low-budget movie, because I know it will be fine financially. So I wasn't really worried. It wasn't make or break for my career. It was something fun and different," he says.