Trust me, a spell won't help esteem issues. You need to look inside and accept yourself.
Personal improvement however is fine and should be done. A beauty spell will not make you instantly look like a model, but if you couple a clear skin chant with a daily face washing routine the changes will be noticable sooner. Weight loss/gain are similar, they work with your exercise and diet to make results appear sooner or reduce cravings.
Beauty spells have also been said to work as an illusion to those around you, you won't see the change, and those closest to you might not, but everyone else might view your nose being smaller, or your skin being clearer [examples] no real physical change has happened, and its only temporary, but that's another way beauty spells are said to work.
If you ask me, try a chant while washing your face or in the shower to help your hair/skin and maybe one if you wish to loose weight, and try to eat healthy and exercise. Most important however, I would meditate, look inside and try to fix your body issues. It's hard, but you will be happier in the long run dealing with these issues than covering them up with quick fix ideas.