After change width and displayWidth, I use body.setSize to change only the height and keep the same width, but (I don`t know why) the width change
console.log(item.body.width); //Show a value of 50 for body.width
var base=50;
item.width=base;
item.displayWidth=base;
item.body.setSize(item.body.width, item.height-4, true);
console.log(item.body.width); // //Show a value of 318 for body.width