Large amount of data in backups after update to Sierra
tmutil offers a compare option which list the changes between two TM backups.

 compare [-@acdefglmnstuEUX] [-D depth] [-I name] [snapshot_path | path1 path2]
         Perform a backup diff.

         If no arguments are provided, tmutil will compare the computer to the latest
         snapshot. If a snapshot path is provided as the sole argument, tmutil will compare
         the computer to the specified snapshot. If two path arguments are provided, tmutil
         will compare those two items to each other. tmutil will attempt to inform you
         when you have asked it to do something that doesn't make sense or isn't supported.


To get a list of snapshots use tmutil listbackups.