Kardashian will front a six-month long campaign that centres around Protein World’s 30 Day challenge, a weight loss challenge for women who want to "feel more confident and comfortable in [their] own skin, lose baby weight, or just show [their] ex what he’s missing".
The brand's chief executive, Arjun Seth, said: "With this campaign we're celebrating empowered young people who want to be their best selves, by looking good and feeling great."
Protein World was previously the centre of controversy over its ‘beach body ready’ outdoor ad campaign, which was accused of making women ashamed of their bodies.
However, Seth was unrepentant about the ad and the advertising watchdog ruled it was not offensive. The resultant publicity from the controversy helped Protein World generate an additional £2m in sales, the brand said.
Protein World has hired independent youth marketing agency ThinkHouse for the Kardashian campaign, having not previously had an agency.
ThinkHouse is Protein World’s first through-the-line agency and will act as lead creative and strategic agency in their "bid for global domination" in 2017.
Jason Yates, the UK managing director at ThinkHouse, said: "We had long conversations with Arjun Seth and his team and they were absolutely ready to embrace change and to focus on female empowerment.
"This is a new day for the brand, it has to move forward, many brands have been associated with issues in the past that they want to move forward from and we believe people and brands deserve a second chance."
Kardashian claims she has been using Protein World’s Slender Blend "for a while now and have grown to love the shakes".
Yates added: "There’s no bullshit with Khloe. She would not do a six-month brand campaign with Protein World unless she was absolutely using it and loving it.
"This was absolutely not about a cynical brand endorsement, this came from the heart."
Kardashian has been interviewed by People magazine to kick off the campaign and will post on Instagram and Snapchat promoting Protein World throughout the six-month campaign, including posts in the summer about how she maintains her workout on holiday.
Creative has been inspired by 80’s classics Fame and Flashdance and focuses on the theme of "feeling good inside".
Kardashian said: "Training can be hard sometimes: remember, if you fall down and if you mess up on your diet don't stay down. You get back up and you say ‘OK tomorrow I'm going to work out a little bit harder’."
Those who sign-up to the Protein World 30 Day Challenge will receive 'exclusive full body workouts' along with a 'comprehensive meal planner'.
Yates concluded: "It is very easy to criticise the word empowerment when you have not had challenges. Let me tell you that as a black male in a predominantly white industry I have faced my own challenges and I’ve been delighted when I felt empowered and my mentors offered me empowerment.
"Empowerment is a great thing to offer somebody and I think a brand that offers people an opportunity to change and improve themselves - if they want to - should be applauded and not criticised for that."