Fixing these involves replacing the elastic. I ordered some 1 inch wide elastic (the original was 1.5 inches wide, but we will make the 1 inch work). I will also eliminate the useless drawstring.
Somewhat to my surprise, you cut the elastic to fit your waist exactly. This actually makes sense if you have hips. If you are shaped like a watermelon, you will have other issues to solve. Then one method is to join the ends with a scrap of fabric using bar tacks and zig-zag stitches. Then mark the 1/2 and 1/4 way points on the circular piece of elastic.
Take the garment apart using a seam ripper. The elastic is typically enclosed in a 1 or 2 way "hem". When you sew in the elastic, stretch it to match the unstretched fabric. Then when you release it, the fabric will bunch up naturally.
If the existing elastic still has enough life in it, you can partially open up the garment, pull out a loop of elastic and shorten it -- but this is not what I intend to do.
The following videos are good, pretty short, and show the game (and more!) --
Here is the elastic I bought on Amazon. 1 inch wide, 12 yards long for $7. 12 yards is enough for 12 sets of shorts. So the elastic is dirt cheap, it is all about the labor. Most of the labor is ripping stitches and removing the old elastic.
Some people say to measure your waist and cut exactly to that. The common advice is to subtract 2-4 inches. One person says they work in the industry and always subtract 2 inches.
I put pins at the 1/4, 1/2, 3/4 points and then pin it into the shorts I am repairing. I debated removing the liner in the shorts, but decided not to.
I did just eliminate the drawstring. I only used the drawstring when the elastic failed, and I always hated using it. Maybe it would save your bacon if you were swimming and diving into the water with people watching.
I sewed it in with one line of stitches, pulling (stretching) the elastic to match the fabric. I have the shorts on, and they seem fine. The fit is quite "gentle" -- I could probably have subtracted 4 inches and it would have been fine. There is lots of extra stretch available when I have them on.
Tom's home page / tom@mmto.org