The Shanghai-native then decided to share health, nutrition and fitness knowledge he has learnt with others. His blogs became an instant success. He has garnered about one million followers on Weibo, and nearly 400,000 on WeChat over the past two years.

As the Chinese government has been looking to entrepreneurship and innovation among the bright spots in a slowing economy, Wang also felt he has found a sweet spot to cash in on the booming demand for keeping fit.

He resigned from his post at a private equity firm to launch a startup company called Fit-start in September, 2014, which happened to coincide with the one year anniversary of his blogs.

"The market has immense potential," said Wang, with over five years of investment experience.

On June 19 this year, Fit-start introduced apps offering custom online workout and dietary plans on the iOS and Android app stores. Wang said there have already been more than 100,000 downloads by now.

However, Wang's rivals have also been looming large. RJFitTime, another influential blog operated by two twenty-somethings, has attracted two million followers combined across all social media platforms. RJFitTime launched apps earlier this year, streaming a variety of exercise programs to its subscribers.

An estimated 50 health and fitness apps came online in the first half of this year. Most of them eye the same niche market as Fit-start and RJFitTime - the beginners.

"When we start our business, the fitness industry was still a 'blue ocean', where the market space is vastly uncontested,' Wang said, "but now, it's fairly crowded."

For users like Zhang, the swarm of fitness apps allows them to get a lot of services for nothing. Zhang said he will not consider trying paid options of those apps, because he thought the free content is already enough.

That mentality is certainly not pleasing to Wang, who has been working hard to bind users with online paid trainers. But the former investment banker is still optimistic about the future of China's fitness market.

"After all, this is a budding industry. The market is huge, and there is no dominant player at the moment, which means everything is possible, " Wang said.