The excessive data consumption is no thanks to the latest update of Snapchat which includes the new “Discover” feature. It seems that apart from the excessive data consumption, the latest update is also said to be buggy as it is crashing frequently, not to mention is draining battery faster than some users had expected.
If you’re running the latest version of Snapchat, you can limit the data it consumes by going to Data Usage in your phone’s settings menu, select the Snapchat app, and check the box that says “Restrict background data” which would basically disable background data as long as you are on a mobile network.
Alternatively you could always try and get your hands on the Snapchat 9.1 beta APK to see if the issue has been fixed, but hopefully this is something Snapchat is looking into and will release an update soon that will optimize its data consumption.