[Kitten]

this should work

pawn Код:

forward EatTimer(playerid);

public OnGameModeInit()
{
    SetTimer("EatTimer",timeyouwant in miliseconds,true);
    return 1;
}

public EatTimer(playerid)
{
    new Float:health;
    GetPlayerHealth(playerid, health);
    SetPlayerHealth(playerid, health - 1.0); // you can change 1.0 to like 5.0 to lose more hp
    return 1;
}