Four words: Food got him pregnant.

Reports Radar Online:

Breakups can be hard on your heart – as well as your body!

After a painful and very public breakup with sexy singer Rita Ora, Rob Kardashian has packed on a whopping 40 pounds, showing off his new fuller figure in Los Angeles on Tuesday – and RadarOnline.com has the shocking photos.

The 25-year-old sock designer was snapped visiting his mother’s Encino office, looking almost unrecognizable and showing off his weight gain in a Jimmy Kimmel Live sweat suit.

Rob, who lost a lot of weight when he was competing on Dancing with the Stars, appears to be back on the diet wagon, however, as he was clutching onto a portion controlled, meal delivery program box and a bottle of water.

Rob admitted in Sunday’s episode of Kourtney & Kim Take Miami that he didn’t take care of his body during his one-year long semi-secret relationship with the How We Do singer, gaining a significant amount of weight during and after their relationship, eating comfort food and not exercising.

“All I did was waste a lot of money and gain 40 pounds,” he revealed to his sisters during dinner.

@ebengregory