The business, which runs 150 gyms, saw its earnings lift by 46% to £28m in the year to the end of December following the completion of its purchase of LA Fitness.
Pure Gym bought LA Fitness for an undisclosed sum, believed to be between £60m and £80m. It ran 43 outlets last May.
The business, which now holds more than 780,000 members, said 20 LA Fitness outlets remain to be converted to Pure Gyms by the summer as part of a £30m investment programme.
It said the acquisition has boosted its presence in central London and the South East of England, adding it hired new senior management as the business grew last year.
The group added that four of the sites it bought from LA Fitness will either be sold off or closed.
Six-time Olympic track cycling champion Sir Chris Hoy joined Pure Gym in June as a brand ambassador, a role that also saw him become an investor in the business.
Pure Gym chief executive Humphrey Cobbold said the group has had "an exceptional year."
He added: "The acquisition of LA Fitness, the strengthening of our management team, the investment in rebranding and launching new initiatives has put us on the front foot for another successful year ahead."
Pure Gym is classed as a budget fitness business, with most of its sites open 24 hours a day, and where members pay monthly fees rather than signing long contract commitments.
The firm was founded by health club veteran and executive chairman Peter Roberts, who launched its first two gyms in Manchester and Leeds in November 2009.