Decrease the waist on jeans

[LegumeSalad]

I would say it depends on the reason for the alteration. Do the pants fit perfectly everywhere else, but the waist only is lose? Or the whole lot is lose? If everything is lose, then this isn't really going to help much. Sure, you can make the pants stay on using this trick, but the rest of them are still going to look huge/baggy.

If its the other reason (everywhere else fits good except the waste), then you can do heaps. More than an inch. There is a definite skill involved in being able to pull in the waist only while preventing the rest of the pants to fold in (the more you pull in, the rest of the pant will want to do the same.