The song reached number one in the United Kingdom, Australia and New Zealand, and number six in the United States BillboardHot 100. Despite charting high, the song did not perform as well as his two previous lead singles, "The Real Slim Shady" (2000), and "Without Me" (2002).
Two skits regarding the Michael Jackson controversy were included on Encore, "Paul (Skit)" and "Em Calls Paul (Skit)". The lyrics to "Just Lose It" refer to Jackson's legal troubles, however he does state in his song "... and that's not a stab at Michael, That's just a metaphor, I'm just psycho...." At the beginning of the song there is a lyrical excerpt from Eminem's 2002 single "Without Me" about how "Shady's back". The line "Snap back to reality. Look! It's B. Rabbit" and "You signed me up to battle" refers to "Lose Yourself" and Eminem's character in the movie8 Mile. In the second verse of the song there is a line "So fellas, fellas..." which is a reference to Sir Mix-a-Lot's song "Baby Got Back". The line "Girl you know you're my world," from the chorus, is a reference to the chorus of his song "Superman" from his album The Eminem Show.
The song received mixed reviews from critics, many of whom found it too similar to Eminem's previous work. AllMusic highlighted the song in a review of the album. Pitchfork was also positive: "Just Lose It" is still most notable for dancing with paedo and homoerotic imagery: It's the one track here that seems as potentially multilayered as the best of The Marshall Mathers LP, yet it's still more curio than anything else."NME wrote a somehow good opinion: "Em (is) reduced to making funny noises to keep things interesting." David Browne of Entertainment Weekly, however, felt mixed: "First [on the album] came the sarcastically bouncy "Just Lose It", a lazy retread of earlier hits that, with its easy-target references to Michael Jackson, made Eminem appear to be the one who'd actually lost it." J-23 panned the song and called it "by far the worst song Eminem or Dr. Dre has ever made. It really seems like their object here was to make the worst song possible. The interlude leading into it is damn hilarious though."
RapReviews argued that it isn't "dropping any jaws or widening any eyes."Rolling Stone described this song as "dance-music dis." In a review praising Encore's "edginess," Steve Jones of USA Today cited the song's mocking of the Michael Jackson child-molestation scandal. Alexis Petridis of The Guardian, however, wrote: "Just Lose It, his plan appears to involve belching and making fart noises, which, with the best will in the world, won't suffice." Kelefa Sanneh of The New York Times wrote the song "unfolds as a series of puzzlingly unfunny jokes."Stylus Magazine was negative as well: "That Em’s brand new tendency to bite himself."
A week after the release of "Just Lose It", Jackson called into the radio show of Steve Harvey to report his displeasure with the video. "I am very angry at Eminem's depiction of me in his video," Jackson said in the interview. "I feel that it is outrageous and disrespectful. It is one thing to spoof, but it is another to be demeaning and insensitive." Jackson continued: "I've admired Eminem as an artist, and was shocked by this. The video was inappropriate and disrespectful to me, my children, my family and the community at large." Many of Jackson's supporters and friends spoke out about the video, including Stevie Wonder, who called it "kicking a man while he's down" and "bullshit", and Steve Harvey, who declared, "Eminem has lost his ghetto pass. We want the pass back." The video was banned on the BET channel, after complaints from Benzino and others (but was later reinstated, as critics of the ban argued that Nelly's "Tip Drill" video could be seen. Both were only seen on BET: Uncut.) However MTV did not drop it, and the video became one of the most requested on the channel.