Whether you have lost weight or simply have loose-fitting pants, the situation can be solved. With a little time and a few supplies, the waistline on a pair of slacks or jeans can be made smaller in a few easy steps.
Try on the pants you are altering and place a safety pin at the desired fit. Mark this spot with dressmaker's chalk. Also mark the point below your waist where the pants begin to fit properly. Remove the pants.
Remove the waistband of the pants by cutting the stitches with the seam ripper. Shorten the waist band by the desired amount, on the sewing machine. Try it around your waist. Move the button to tighten the waist further, if necessary.
Remove extra material from the back and front of the pants by adding darts. Mark the placement of the darts on the inside of the pants using dressmaker's chalk. Draw a straight line where the dart will be, from the waist down to the area where the pants fit correctly. From the center line, draw two sloping lines to create a triangle where the darts should go. Pin the darts and try on the pants to make sure the new shaping is correct.
Sew the darts in and clip the extra threads. Try the pants on once more before stitching the waistband to the pants.