Food is not a buff. Meads and rested are buffs. If you log off all buffs are removed when you log back in. I believe that is intentional to prevent you logging out when your rested buff expires (at night in hostile territory) and you log into another world and rest in warmth and safety, get the buff, and go back. Losing buffs when you log off prevents this exploit.

The devs also changed (this expansion) how stamina regenerates after logging off. Its still possible to game it, it just takes longer now.