It turns out that fans of Kim Kardashian are not the only ones who respond in a positive way when she mentions a product on Twitter and says, “Buy this.”

Sports fans who follow their favorite athletes on social media are 55% more likely to purchase a brand if an athlete mentions it on Facebook or Twitter. That impact is even higher among young (18-34), non-white fans (75%) and those with kids at home (62%), according to the just released 2011 Catalyst Fan Engagement Study.

The study, conducted in May, included more than 2,000 people who identified themselves as sports fans. It focused on the social media attitudes and usage habits of NFL, NBA, MLB, and college football and basketball fans in particular.

The survey did not mention which athletes had the most influence via their Twitter and Facebook destinations. However, among the most active on Twitter and with the largest number of followers are Shaquille O’Neal (nearly 4 million), Serena Williams (more than 2.1 million followers), Chad Ochocinco (2.1 million), Dwight Howard (2 million) and Paul Pierce (more than 1.8 million followers).

What the study did show is how social media has created more of a one-on-one connection among fans, athletes and teams.

“Social media is an increasingly powerful tool for marketers to reach sports fans in a very authentic way,” Bret Werner, managing partner for Catalyst Public Relations, NY, said in conjunction with the release of the report. “Fans who use social media are more passionate and engaged with their favorite sports, teams and especially athletes. The strategic alignment of attributes between brands and athletes – ensuring relevancy and authenticity – will have a greater impact on driving purchase.”

Among the keys points uncovered by the survey:

• People who follow NCAA basketball are the most digitally connected.  NBA fans were second.
• 80% of fans use Facebook, 30% use YouTube and 23% use Twitter to follow athletes.
• People are likely to participate in fantasy leagues, purchase brands mentioned by athletes, and say they have become even more involved with sports since they started using social media to follow or discuss their favorite sports.

Young, non-white fans engage with their favorite athletes, teams, sports – and fellow fans ¬– through mobile devices and social media channels more than any other demographic group. According to the survey, they are more likely to use social media to meet people with similar interests, and to share information and pictures with other fans.

Within this group, 81% have experienced at least one of the following in the past six months: watched sports live on a laptop, tablet, mobile or smart phone and used any location based services to enhance the viewing experience. That is compared to compared to 51% of all fans who participated in the survey.

According to Shripal Shah, svp-digital for Catalyst Public Relations, “With the growth of social media channels like location-based services and mobile devices, fans can connect, share, create content and build communities with each other, more than ever before. It creates a richer experience for the sports fan, and, when done properly, brands can add to it.”