I will have to admit I think this website is pretty fun.
You put in your current weight and then the weight you want to be and it populates an image of the difference.
You have several options to customize your sim to make it as close to you as possible.
After you have made all of your custom choices, you get a side by side comparison as well as the option to turn your sim in all the way around to view both the front and the back.
Here is the one I did of me:
The website can be found here. Go have some fun!