LA Fitness flew into a Twitter storm after Guardian's consumer champions took up the case. Now all gyms are under pressure to improve their contracts

It was one of the most distressing cases of a reader in trouble that Guardian Money has ever had to deal with. But it resulted in an overwhelming outpouring of generosity from readers that led – belatedly – to a humble apology from the company at the heart of the storm. What's more, gym-goers across the UK may benefit as the Office of Fair Trading promises a crackdown on unfair contracts.

It began last Saturday when Guardian Money's consumer champions published a letter from a reader, Hannah, in Essex, a heavily pregnant woman whose husband had just lost his job. She had written to us in desperation having reached breaking point over a dispute with gym chain LA Fitness, after moving 12 miles away, and she didn't drive. "We are now on benefits. We can barely feed our children and can't afford the two-year contract," she said.

The couple had 15 months left to run on their contract with the gym and were finding it impossible to pay. The Guardian's consumer champions then spent weeks going back and forth with LA Fitness, initially arguing the case on compassionate grounds and then using legal arguments related to the contract itself. The gym chain eventually agreed to waive six months of the outstanding contract, but this left Hannah and her husband still owing £360 – money they simply didn't have.

But within hours of publishing the story, emails started to arrive in our inbox, then the phone calls started and the letters came. Guardian Money readers were up in arms. Many wanted to pay either part, or all, of the couple's remaining costs.

"I was struck by the cold attitude of LA Fitness. Can you please tell the couple I would be happy to pay their gym fees for the next six months if that would help relieve the pressure on them?" said JP of Gloucester, reflecting the sentiment and generosity of the many other readers who contacted us.

Our consumer champions then went back to LA Fitness and, armed with your letters and a few choice words, the company, at last, agreed to drop the remaining charges.

"We appreciate that this is a unique situation and that the couple are undoubtedly going through a very difficult and distressing time," it said in a statement. "We appreciate that their circumstances have changed dramatically since they first signed with us, and on this occasion we will waiver any further membership fees with immediate effect."

But that was not the end of the tale. On Tuesday, the story was posted on Twitter by the Guardian's deputy editor Katharine Viner – a move that resulted in an extraordinary storm of protest.

Thousands of people, including celebrities such as comedian Dave Gorman and DJ Danny Baker, posted messages on Twitter expressing their disgust with the gym.

"If you're a member of LA Fitness, read this [the Guardian Money story], cancel your contract and pass it on. Let's make sure they lose thousands," tweeted Owen Jones, author of Chavs: The Demonization of the Working Class.

Others responded by doing just that. "Just wrote to LA Fitness and ended my membership. DD [direct debit] cancelled. Let them sue us all," one said.

By the following day, tales from other readers had started to pour in to our inbox telling of similar, if less harrowing, tales of problems with their gym. These are only the tip of the iceberg: The Office of Fair Trading said that it received about 1,500 complaints about gyms in the four-month period to December last year.

The OFT has now told the Guardian that it will crack down on gym contracts that customers cannot cancel, in an announcement to be made next week. Although it won't divulge any details yet, the watchdog is likely to focus on long-term contracts that do not allow members to cancel if their circumstances change.

Last year the OFT won a landmark case in the high court against Ashbourne Management Services, a company that draws up agreements and collects payments from gyms, and has more than 500,000 customers.

Ashbourne's contracts had minimum membership periods of between one and three years and Ashbourne routinely stated that consumers could not terminate their membership. After a four-day hearing, the judge in the case ruled that, among other things, a contract was unfair if it was for longer than 12 months and did not allow the consumer to cancel with 30 days' notice and pay a moderate sum in compensation.

The ruling only applied to Ashbourne, but the OFT warned at the time that it would have wider implications for the whole gym industry.

"We are clamping down on this [unfair terms in gym contracts]," said Nigel Cates, a director in the goods and consumer group at the Office of Fair Trading. "We have already given gyms six months to look at their contracts after the Ashbourne ruling last year. We are following that up. We don't want any of the same circumstances to happen in other gyms."

Hannah, meanwhile, was overwhelmed with the response from Guardian readers.

She is due to give birth in two weeks and said the news could not have come at a better time. "I'm quite gobsmacked," she said. "You have no idea how grateful we are to you and all those people who wanted to support us. You have been a complete answer to our prayers."

So what should you do if you have a problem with your gym?

If your circumstances have changed since you took out your gym contract and you find yourself unable to pay or use the gym for any other reason, talk to your gym, regardless of what the contract says. Although the Ashbourne judgment only applies to contracts drafted and recommended by Ashbourne, the OFT says it would expect businesses using similar terms to refrain from enforcing terms in existing contracts which are unfair. This is especially the case with contracts that are more than a year long.

If you can't get redress on your own, check if your gym is a member of the Fitness Industry Association. This has a code of conduct that members must adhere to. You should also report the gym to your local trading standards service and, in the last instance, use the small claims court.