shrink physical volume

[zio_mangrovia]

In VMware ESXi 5.5 I have Centos 6.8 64 bit with hard disk of 60 GB which is partitioned into two partitions:
/dev/sda1 partition, 512 MB, type: Linux 83 (boot partition)
/dev/sda2 partition, 60 GB, type: LVM 8e

/dev/mapper/vg_centos is the volume group which has /dev/sda2 physical volume
I have has 2 logical volume: lv_swap and lv_root.

How can I shrink physical hard disk (e.g. from 60 GB to 45 GB) without to lost data, particularly LVM partition /dev/sda2?
I tried by Gparted, before disactivating volume, but nothing!
I can power off server if it's necessary of course.

[aks]

The order to do it in is:
1) Shrink the filesystem (depends on the FS used).
2) Reduce the volume (lvreduce)
3) Reduce the VolumeGroup (vgreduce)
4) Resize the physical (pvresize)
Oh and at 0) Backup everything.