Researchers from the National Institutes of Health in the US analysed over a million social media posts and comments about weight matters.
The study was one of the first to analyse how weight is discussed on various social media channels such as blogs, Twitter, Facebook, forums, Flickr and YouTube, researchers said.
Wen-ying Sylvia Chou, lead author of the study and co-author Abby Prestin analysed 1.37 million posts in the sixty days between 23 January and 23 March 2012, all containing the keywords 'fat', 'obese', 'obesity' or 'overweight'.
On the other hand, dialogues containing the terms 'obesity' and 'overweight' generally include more information, such as hyperlinks to news articles or healthcare agency websites.
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Although blogs and forums produce a small volume of posts, they can support in-depth, sustained online exchanges about weight-related topics, including helpful information about healthy eating and weight management, the study found.
Researchers said that 1.25 million or 91 per cent of all the relevant posts analysed are found on Twitter. One in every three of the top relevant retweets contains 'fat jokes' or music lyrics which especially stereotype women of certain physiques.
Taken together, a large proportion of user-generated content on social media reflects and reinforces weight stigma.
Pervasive negative stereotypes and jokes abound, as do examples of the alienation of overweight people and self-deprecating humour, researchers said.
Even more alarmingly, such negative sentiments extend to verbal aggression, with far too many unchecked instances of flaming and cyberbullying against overweight individuals, particularly women, they added.
"Twitter and Facebook posts are dominated by derogatory and misogynist sentiment, pointing to weight stigmatisation, whereas blogs and forums are safe online havens that provide support against weight bias," Chou said.
The study is published in Springer's journal Translational Behavioral Medicine.