Edit in JSFiddle

// Phaser version 2.4.8
// HealthBar 

var game = new Phaser.Game(600, 400, Phaser.AUTO, 'test');

var BasicGame = function(game) {};

BasicGame.Boot = function (game) {};

BasicGame.Boot.prototype = 
{
   	create: function() {   
    
   		   var bmd = game.add.bitmapData(200,40);
         bmd.ctx.beginPath();
         bmd.ctx.rect(0,0,180,30);
         bmd.ctx.fillStyle = '#00685e';
         bmd.ctx.fill();
        
         healthBar = game.add.sprite(game.world.centerX-100,game.world.centerY,bmd);
         healthBar.anchor.y = 0.5;
    },
    
    update: function() {
     barWidth = healthBar.width;
     LIFE = 40;
     healthBar.width = barWidth - barWidth/LIFE;
    },
};

game.state.add('Boot', BasicGame.Boot);
game.state.start('Boot');

<div id="test"></div>