Are you talking about truncating or shrinking?

Truncating is only applicable to log backups.

Shrinking can apply to data and log files but not backup files.

If the backup file is 60GB, then that is how much data is in the database. The only way to reduce that is to clean out data from the database, which may or may not be appropriate. If the size of the backup is an issue, there are 3rd party tools which can compress them on the fly (e.g. RedGate SQL Backup or Quest LiteSpeed)

If your database is still growing, then shrinking is not a good idea - it will just grow again anyway.

If the log file got blown out for some reason, preferably one that is not going to reoccur, you could shrink it. Lookup DBCC SHRINKFILE in BOL.