Newcastle Knights cult hero Adam MacDougall is reportedly swimming in cash after his Man Shake nutrition company was flooded with a $400 million investment.

The 46-year-old has sold a majority stake in his Crazy Health company to Australian investment giant Pacific Equity Partners.

He is now instantly one of the richest men in rugby league — and instantly one of the greatest post-career fairy tales the sport has known.

The Daily Telegraphfirst reported PEP has coughed up more than $400m to secure a controlling stake in the weight loss and sports nutrition empire MacDougall built from his garage with wife Belinda.

The Financial Review reports the investment firm valued the company at around $200m before splashing the cash.

MacDougall finished his 16-year professional career with 195 first-grade games, 11 Tests, 11 State of Origin matches for NSW and two grand final victories — but the buyout from PEP made public last week is his biggest ever.

This is a real rags to riches story,” MacDougall told The Telegraph.

“I started this business in my garage with my wife and to have a company like PEP choosing to invest in us is fantastic.

“I won’t deny we have done pretty well financially out of it. But we remain fully invested in the business and will still be working in it every day.”

His empire is far from an overnight success story.

His path towards a fitness empire was already beginning to take shape before he finished up his career in 2011.

He studied at Newcastle University part-time for 12 years and gained a Master of Business Administration degree, a Bachelor of Economics and a Masters of Business Coaching.

At the time of his transition from the football field to the business world, he made a series of investments in mining and real estate and also started a sports equipment company with Belinda that grew to have more than 120 employees before selling their stake in the business.

He told The Newcastle Herald in 2013, exactly how he got the inspiration for the Man Shake — a lightning bulb moment that ended up being a $400 million idea.

He said he ended his career doing public speaking gigs and motivational corporate talks and soon discovered a repeating theme of men struggling to maintain their fitness operating in the real world.

“The corporate-type people I was bumping into were too busy to look after themselves,” he said.

“Whilst a lot of these guys were making good money, they weren’t eating right or getting enough exercise.

“The more I looked into it, the more I realised men’s [poor] health had become an epidemic. “Around 75 per cent of Australian men are either overweight or obese. When I started researching it, I quickly realised that for busy people, diet was the most important thing. Even for people who are able to get regular exercise, it’s all about what you put in your mouth.”

He decided to do something about it and says he consulted with a food scientist, a nutritionist and a doctor in developing the formula for his weight loss products, highlighted by the Man Shake and Lady Shake.

The Telegraph reported in 2016 MacDougall sold everything he had to get the company up and running.

He said at the time he had spent $250,000 on product testing and focus groups alone during a six-month product development phase.

I started making my own shakes,” he said.

“I was putting all this stuff in them - fibre, flaxseed, green tea, whey - and I suppose it was a bit cumbersome.

“Then I spoke to a food scientist, a nutritionist and a doctor and got some ideas. I was passionate about being active and living a healthy lifestyle, and that’s how I came to create the Man Shake.”

It began as a small-time local online business that grew quickly. The next step was deals with local chemists before deals were struck for his products to he stocked as major national chemist and supermarket chains.

The next step — he and PEP believe — is international growth.

The firm has considerable experience in managing the growth of consumer products with interests in a number of international businesses, including New Zealand health products company Manuka Health and the parent company of Four N Twenty pies, Patties Foods.