Aug 19, 2011 14:22 GMT  ·  By

Since Jennifer Aniston went public with her romance with co-star Justin Theroux, tabloids have been keeping busy. A new report claims that her ex, John Mayer, is still pining away for her – while packing on the pounds.

Aniston and Mayer ended their relationship on less than an amicable note, when he called up the paparazzi and held a press conference in the street to announce he’d broken up with her.

Now that he sees her so happy with Theroux, Mayer is dying slowly on the inside, the latest print issue of Us Magazine claims (story via here).

“A source says the singer, who put the final kibosh on his one-year romance with Aniston in March 2009, still pines for her,” the publication writes.

Mayer simply can’t forgive himself for killing every chance he ever had with Aniston, the insider says.

“She was the one who got away. He’s definitely not thrilled to see Jen in so many photos with a new guy – especially one who is a cooler version of him,” the spy explains.

Not only is Theroux much cooler than Mayer but, according to Us, he’s also in better shape, especially since the singer has been packing on the pounds in recent months.

“Now spending his time gorging on pizza bites, Hot Pickets and Smucker’s Uncrustables while writing new tunes in his home in L.A.’s Pacific Palisades, Mayer, 33, is ahem, heavy with regrets,” the mag writes.

In other words, Mayer is drowning his heartbreak and frustrations in junk food and music but still, every time he sees a photo of Jen with her new man, the pain is back again.

“He’s just eating microwave food and getting chunky. Seeing Jen happy now isn’t easy. He cared about her more than any of his other girlfriends,” the unnamed source explains.

One month ago, another report claimed that, deeply upset and regretful, Mayer was calling Aniston on a regular basis trying to convince her to take him back, as we also noted.