These stunning before-and-after photos are helping an Instagram star launch a fitness empire

You may not know her by name but you probably have seen her workout videos pop up on your Instagram feed.  

Kayla Itsines is a social media star and trainer who has built a massive empire with millions of followers.

The 25-year-old Australian has become Instagram-famous with her Bikini Body Guides. She also has an app that essentially puts her training in her fans' pockets.

The star has cultivated an online community that calls itself "Kayla's Army," largely by sharing impressive progress photos - or "transformations" - of the women who are committed to her program. It serves as visible inspiration.

These are some of the photos Itsines has shared: