Gilchrist has since ploughed much of that windfall into the fast-appreciating Sydney and Byron Bay property markets.

Together with his earlier success in selling a mobile storage company, Zippy Shell, and prior to that an e-payments service to a publicly listed company, the Rich List research team estimates the entrepreneur’s gross wealth at more than $600 million.

Deutsch, who departed F45 in February last year after what’s understood to be a falling out with Gilchrist, has also accrued a nine-figure wealth from co-founding F45.

In addition to the $61 million he received upon Wahlberg’s entry to the franchise, on October last year, Deutsch sold his remaining 28.6 per cent stake back to F45 for $US143 million, plus a $US2.5 million bonus on the way out.

That puts Deutsch’s gross wealth around $260 million, an extraordinary return on the redundancy cheque that the former equities trader received from Royal Bank of Scotland in 2011, before ploughing it into that first gym.

A third Sydneysider to become a multimillionaire thanks to F45 is its head of US expansion between 2014 and 2020, Marc Marano.

His 10 per cent stake in the business earned him a $US10 million payday when Wahlberg invested in 2019. Marano departed around the same time as Deutsch, earning another $US32 million by selling his shares back to F45.

Marano turned 40 in March, so his estimated total fortune of $48 million should put him on the Financial Review Young Rich List – which ranks Australia’s most successful 40-and-under entrepreneurs – when it is published on October 29.

Despite its growth, Gilchrist told The Australian Financial Review that F45’s niche remained the same today as when it started – a “functional training workout” priced between a standard gym membership and one-on-one personal training sessions.

F45’s filings show it lost $US25 million in calendar 2020. However, Gilchrist said 91 per cent of its studios had reopened by the end of June (prior to the latest Australian lockdowns) and that growth was back on the agenda.

“Over the next 12 months, we believe there is a significant opportunity to meaningfully expand our footprint in the US and continue to grow our international presence through our existing franchising strategy,” he said.

“In addition, there is a significant opportunity for F45 to expand into new channels, and we are actively pursuing potential opportunities to partner with major universities, hospitality operators, corporations and military facilities.”