gistfile1.js

$('.bxslider').bxSlider({
	pagerCustom: '#bx-pager',
	mode: 'horizontal',
	startSlide: 0,
	controls: 'false',
	onSlideAfter: function($slideElement, oldIndex, newIndex) {
		
		var newClass = $slideElement.attr('class');
		var oldClass = $('.bxslider li')[oldIndex].attr('class');
		
		$('body').removeClass(oldClass);
		$('body').addClass(newClass);
		
	});
});