Excerpt from this article:
Researchers from the Brunel University in London have conducted a study as to why so many people share every workout on social media. The results are unflattering, to say the least.
…People who are always keen on documenting their gym activities (or every time you simply go for a good, old-fashioned run) tend to be narcissists. According to the researchers, the primary goal is to boast about how much time you invest in your looks. Apparently these status updates also earn more Facebook likes than other kinds of posts.