The firm is focused on reopening sites in England from April 12 and April 26 in Scotland and said it has retained more members during the current lockdown than previously.
It added that 97 per cent of current members say they expect to return to the gym as soon as possible, with 75 per cent saying fitness will be more important to them than before the pandemic.
The slump into the red follows a £6.2m profit in 2019, with revenues falling 47 per cent in 2020 to £80m.
Chief executive, Richard Darwin, said: “During 2020 we demonstrated the resilience of our business and its culture even in the most challenging of times.
“By freezing subscriptions when closed and by providing an excellent Covid-secure environment in our gyms when open, we have retained most of our members.”
He added: “We are ready to start rebuilding our membership levels and growing our estate from April 12, extending affordable fitness at a time when health and fitness has never been more important.”
Revenues fell due to 45 per cent of trading days in the year lost due to closures, alongside reduced membership.
Despite the falls, the company plans to open three new gyms in April and one in May. Six leases have also been signed for new sites, with more in the pipeline.