According to Ofcom, 90 per cent of 16- to 24-year-olds have a smartphone, spending between six and seven hours a day on them – of which an average of 90 minutes is spent on social media sites. So social media is very likely to be having an impact on their behaviour and their attitudes.

Encouragingly, Department of Education research has shown that engagement in risky behaviours among young people – such as drinking, smoking and drug taking – has dropped significantly in recent years, while teenage pregnancy is down an enormous 45 per cent since 2007. It’s good to see that obesity rates among young people are also stabilising.

While the reduction in risky behaviour is encouraging to see, what we’re also seeing is that young people are spending more time indoors and alone than ever before, so physical networks are being replaced with online social networks.

With Instagram and Snapchat, social media has become more visual. The selfie trend has made young people think of themselves as permanently on display and they’re now constantly bombarded with images of how they should look.

So it sadly isn’t surprising that, according to NSPCC figures, between 2013 and 2014 the number of children seeking counselling for eating disorders rose by 15 per cent, with 21 per cent reporting to have body image issues.

Given the allure and reach of social media, it’s important for fitness operators to understand that it’s a powerful way to engage with their customers, and potential customers – but it’s absolutely crucial to use responsible imagery and give credible advice. The industry needs to be in this space, but in a highly responsible way.

Social media is a good method of communication, with a big reach – and it’s free – so it makes sense to use it to promote activity and healthy eating. If the message is pitched right, there’s potential to use social media for behaviour change as it builds momentum.

However, it’s important to be mindful about its use so people don’t feel blamed, shamed or guilt tripped, as this can build resistance to making a change.

Content must be interesting, useful and engaging, with imagery that reflects everyone in society, including disabled people – not just photogenic people wearing lycra. It’s also vitally important to get facts right and, when posting photos and videos, the technique that’s shown has to be perfect.

Operators should be careful not to sell too hard, because pushing diet food, pills and meal supplements can be a turn-off and won’t promote healthy long-term behaviour. However, if clubs use encouraging messages presented in an accessible, fun way – “have you tried this workout yet?” – it can work well.

Social media has the potential to be very supportive, but can be part of the put-down culture too. With cyber-bullying an issue, and teenage suicides happening as a result, it does concern me that there’s a potential for people to respond negatively to a post. This could have a significant impact on self-esteem, especially among vulnerable people.

Currently I think that social media is working well in reinforcing the good behaviour of those who are already converted, but as an industry we need to keep working to engage with those who aren’t exercising at all.

Social media is a powerful tool and an undeniable force in modern society, but it’s not a magic bullet. Social media reflects trends and behaviours that are already going on in society rather more than it has a hand in shaping new ones.

What it can do is allow a two-way conversation, and it’s a proven way to build communities. This creates a good opportunity for the fitness industry to be at the centre of lifestyle changes.

Using social media to celebrate the successes of members reaching fitness milestones, however small, could be very supportive and effective; for the member, there’s more value in having the club celebrate their achievements than in celebrating themselves. This presents the club as friendly and welcoming and, if it goes onto the member’s timeline, can reach an audience of people who are currently not engaged with fitness.

If your club caters for a number of different markets, sub-divide groups and the messages – what’s appropriate for a 40-something mum looking to tone up after having kids won’t interest a teenage bodybuilder. Create communities of like-minded people where they can share their hurdles and hiccups and support each other.

The messages need to be focused on selling the benefits of exercise and being motivational and fun. The issue of body image is a sensitive one in today’s world and clubs should avoid appearing to put pressure on people to look a certain way.

Video content is being favoured by many of the social media platforms – Facebook is more likely to display it in people’s news feeds, for instance – and it’s highly appropriate for the health and fitness market, so operators need to get on board with this medium.

Finally, Facebook was originally seen as free media, but it isn’t now. Organic reach of posts to page fans – people seeing your updates for free – has dropped to a tiny percentage.

If operators want to reach new audiences, to engage people who are currently inactive, they will probably need to boost their posts or, even better, use Facebook Targeted Advertising, which can be highly effective. Adverts can be aimed at people who have expressed an interest in health and fitness, are of a certain age and live within defined geographic areas.

People are influenced by social media at least as much as they are by old media now, and it’s very easy for us fitness professionals to get on it and share our messages. I get messages every day from people letting me know the tips and advice I post online have helped them.

In my latest 12-week fitness programme, Forge, I’m using social media to add another level of accountability, because most people are much more likely to follow through on what they start if people are watching. Participants post details of their goals on their social media channels, promising an update at the end of the 12-week programme.

It’s true that when we get fitter and healthier, it can make people look at their own lifestyle and feel bad about not taking better care of ourselves. But that’s definitely not a reason for us to keep quiet about it. Hiding our achievements, or pretending not to enjoy exercise, will not help those people at all. Sharing inspiring posts, pictures and comments about the amazing benefits fitness brings to all areas of lives just might help them work through that negativity and start something that could dramatically improve their lives.

 Motivational tips and images have their place, but don’t neglect to publish real practical advice that people can put to use. The wonderful thing about social media is that it’s about two-way interaction. So listen to your community, ask them what they need help with, and notice what type of content they engage with the most.