My quest for jeans that fit at both the hip and the waist has finally brought me...here.
I've removed the rear center belt loop, and ripped the waistband from the back yoke. These are Uniqlo stretch high-rise straight leg jeans bought online about 2 or 3 years ago. They were about 5 cm too loose at the waist, even though they fit just about right (not too loose, not too tight) at the hip. To be on the safe side, I decided to take in 4 cm at the waist. I put 2 darts on each side of the yoke, and then I stitched the waistband in 4 cm at the rear center. Then, I stitched the waistband back to the yoke, and replaced the belt loop. The last part was the most difficult, because 2 layers of belt loop (2 layers of fabric x 2) + 2 layers of altered waistband (2 layers per altered layer x2) meant that the machine was stitching through 8 layers of denim. I was pretty much yanking the fabric through the machine.
So the stitching is a little crooked and the back center belt loop is a little low. But now, even without a belt, I can get by without having to hike them up every 30 seconds.
Once I got started, the whole thing took about 3 hours.
The only thing is, it took about 3 months to get started.