Rob Kardashian has reportedly lost more than 15lbs.

The 28-year-old reality TV star - who piled on an estimated 100lbs in just 12 months - has already dropped an impressive amount in weight by following a gruelling exercise plan put together by celebrity trainer GUNNAR PETERSON after vowing to fight the bulge once and for all.

A source told Us Weekly magazine: ''He's already lost more than 15 pounds. Rob has been sticking to the plan Gunnar created for him, and is getting meal delivery from a chef.''

But it's not just Gunnar pushing for the sock designer to see results as his famous sister Kim Kardashian West, 34, took her sibling out for a hike last month after the pair, who fell out last year, laid to rest their differences and made up.

It's also thought Kim's husband Kanye West, 38, has been the leading force in Rob's positive change in attitude after he gave him a stern talking to and offloaded some advice.

An insider added: ''It's Kanye working his magic. He's been a great motivator for Rob.

''He told Rob how he got into shape after his accident and at a time when he was down in his life.''

The unnamed friend believes the sock designer's determination to shape up is in preparation for his return to the spotlight after spending a year shying away from the public eye and refusing to star on his family's popular E! reality TV show, 'Keeping Up With the Kardashians'.

Rob has also returned to social media in recent weeks posting several images of himself on his Instagram account.