Fat suits as additions to costumes on Halloween or any time a masquerade party is thrown are a hilarious way to enhance your outfit. Clowns, sumo wrestlers, dirty old men and other costumes are more believable by adding a bit of padding to give the appearance of obesity. Making your own fat suit is not difficult, but be prepared to be hot and tired after dragging around all the extra padding and weight during the evening.
Decide on who you want to be at the party. Hobos, crooked politicians and many other character costumes leave more of an impression with additional padding.
Search thrift stores and yard sales for large sized clothing, as suggested by the Extreme Pumpkins website. The bigger you can find the better. If you want to appear as a sumo wrestler you should find a top and trousers in a white, off white or beige colour to look like skin colour. Appearing as an ageing prostitute, you would need to find a flashy, large print dress with a silky fabric. Keep in mind what kind of character you wish to represent in your clothing choice.
Purchase some foam sheeting that is about one to two inches thick (such as those used to add comfort to old mattresses) or quilt batting to glue into your outfit. You can find this at major discount or fabric stores. You can even find very inexpensive pillows at thrift stores and use them inside your outfit.
Turn your outfit wrong side out. Glue the foam inserts or old pillows onto the wrong side of the fabric. This will create an obese look. You may have to cut the foam into strips to fit it into trousers or to create the look of sagging breasts in a dress.
Turn your outfit right side out and slide it on. It will be difficult for your trousers to stay up, so be sure to add a pair of suspenders or a large belt. If a belt large enough to fit around your fat suit is hard to find, you can make a sash out of wide fabric ribbon or a long scarf and tie it around your waist.
You can use fiberfill, foam packing peanuts and other types of stuffing inside your outfit, by placing bunches of it in plastic bags, tying a knot in the top and pinning it into the inside of your outfit with safety pins. You can make a sumo wrestler costume by cutting the legs off a pair of old black trousers and forming them around you like a big diaper. Use one around the waist area and safety pin it in place. Use the other trousers leg to cover the crotch area. Safety pin it to the rest of your costume.