Rob Kardashian is speaking out against those criticizing his weight gain.

"So i found out i was trending [online] for being fat... thank you all it really made my day :)," the reality star tweeted on Tuesday.

The online hate came after Kardashian, 27, was photographed on Monday at LAX Airport en route to sister Kim Kardashian's upcoming Paris wedding, the first time he was seen in several weeks. The photos prompted some speculation that he'd been out of the public eye seeking help -- a claim he disputed.

"And to the blogs saying i went to fat camp or rehab LOL then why am i still fat u fools?? y'all must have run out of real news," he wrote.

He added: "I'm aware that I'm fat that def aint a surprise to me lol and my only therapy will be in the gym anyways had to say somethingggggggggg."

Kardashian has publicly shared his struggle with his weight on E!'s "Keeping Up With the Kardashians."