Rob Kardashian is always at the gym.

The reality TV star - who shys away from the celebrity spotlight - is on a mission to get back in shape after reportedly gaining 100lbs lately and his personal trainer GUNNAR PETERSON has insisted the star is working hard at it.

He told People: ''Rob is always in! He's slammed schedule-wise and still makes this work.''

Gunnar made the comments after an expectant Kim Kardashian revealed she is helping her little brother get back in shape.

Yesterday (25.08.15) Kim, 34, shared on Twitter: ''Rise & Grind! Workout time!!!!! With @robkardashian (sic)''

And last week she added that the pair have been taking hikes together.

She said: ''Just went on the hardest hike ever today with @robkardashian. (sic)''

Rob, 30, has stayed out of the spotlight and away from his family's fame for almost two years.

That could be about to change as his sister Khloe, 31, said earlier this year that her brother is trying to get his ''groove'' back.

She said: ''Rob definitely has his ups and downs, and he's been struggling for the past year and a half, maybe two years, which I think we've all had those times in our life.

''He's been doing better, but I want Rob to do consistently forever. So right now I'm really proud of him.'