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In the moments before a recent interview with Best Coast’s Bethany Cosentino, the YouTube advertising lead-in for her “Feeling OK” video involved the buttermilk crispy chicken sandwich at a certain well-known hamburger chain. This wouldn’t have been noteworthy, except that the “Feeling OK” video is about the jumbled-up anxiety that can lead to intense exercise and an obsession with healthy eating.

“Um, I don’t really have a comment on that,” Cosentino says. “I do appreciate a little McDonald’s now and then, especially when you’ve had a little bit to drink. It can help with the headache. But that’s funny, that it came before an exercise video. Maybe it was meant to inspire people.”

A little irony about burgers can’t fully capture the complex feelings behind the “Feeling OK” song and video. Cosentino, 28, was diagnosed with an anxiety disorder some 15 years ago, and her compact rock ‘n’ roll songs often deal with spinoff issues like insomnia and struggles with confidence. In the video, the tattooed, leotard-clad Cosentino smiles as she indulges in aerobics and exercise bikes, but her bandmate, Bobb Bruno, undercuts the behavior on a yoga mat surrounded by burgers. It’s upbeat and catchy, but Cosentino concludes in her deep-voiced deadpan, “When I get down, I get so down.”

“The song itself isn’t really about diet and exercise. It’s just about being in a place where I felt like I’d reached this point in my life where I was starting to feel OK and content with the way things were going,” she says by phone from her Los Angeles home. “I’d been dealing with just everyday weird feelings of ‘What does it all mean?’ I can say exercising helped with that a lot. When I go and exercise, afterward I feel a lot better.”

Before meeting Bruno and forming Best Coast as a duo that plays fast, short, murky songs on the border between Liz Phair’s “Exile in Guyville,” the Beach Boys and the Shangri-La’s, Cosentino tinkered with several forms of show business. As a kid, she acted in commercials, and songs she’d written as Bethany Sharayah spread quickly from her MySpace posts to inquiries from major record labels. Back then, she wasn’t ready to be a pop star, but she kept writing and working in bands until a fateful 2005 LA party.

The party was weird — according to the Independent, a reveler tried to jump out of a window — but Cosentino and Bruno came away with a pop culture connection. “We bonded over bands and TV shows. … When I started writing songs for Best Coast, I sent him some, and I told him, ‘I want to start a band, and you’re the person I’d like to do this with,'” she says. “He heard the demos and said, ‘I love this. I want to do this.’

“Bob and I are both people who are very passionate about what we do, but we also like to have our space. We don’t write together. We don’t write in the same room,” she continues. “I’ve called him my platonic twin flame, because it’s like he understands me. … When you find a dynamic that works, I think best to just stick with it.”

Best Coast’s debut, 2010’s “Crazy for You,” opens with the line “I wish he was my boyfriend.” The album sounds upbeat, but there’s an underlying discontent that suggests something more sinister: The boy in “Boyfriend” has another girl, the love is almost never requited, and Cosentino sings, “I’m always crazy when I miss you” and “my highs are high, my lows are low/ and I don’t know which way to go.” This year’s “California Nights,” the band’s third album, captures this same quality; at the beginning of the album, Cosentino’s feelings skew toward “OK” and “fine,” but by the end she is chronicling sleepless nights and LA’s unique darkness.

“The light-and-darkness dichotomy and all the rest just made sense to me at the end,” she says. “It makes a lot of sense for who we are as a band, in terms of putting forth this happy-go-lucky, sunny-sounding music with these lyrics that aren’t necessarily so happy-go-lucky.”

In the interview, Cosentino seems at peace with her anxiety: “Whenever I meet a fan who says, ‘I deal with anxiety, too, and it’s really bad,’ I always tell them it sucks, but you can always be in control of it.”

She also seems at peace with her insomnia. The other night, she was awake at 4 a.m., and decided to listen to an album by the Primitives (who made 1988’s fantastic “Crash”) before writing and recording a new song with her iPhone. But she hasn’t yet started on the follow-up to “California Nights.”

“I definitely know that inspiration will strike, and when it does I will totally follow it and go with it,” she says. “For now I’m trying to be in this moment and not think too much about the future of things. When the time is right, it’ll all hit me all over again.”

Steve Knopper is a freelancer.

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When: 7 p.m. Friday

Where: Metro, 3730 N. Clark St.

Tickets: $25; 773-549-4140 or www.smartbarchicago.com