I think you can buy anyone under 18. I'm 17 and I bought a few before. The ones I like are the curbing appitite ones. I dont think diet pills really help shed pounds but if they make you not hungry, that can help a lot in the long run. I did it for about 2 weeks with some cheapo curbing appitite pills and I lost about 6 lbs and didnt put it back on.
-fish oil supplements
-a good multivitamin
-chromium poly.... something(not picolinate)(can;t remember the name right nowsuppresses appetite
-2 tbps apple cider vinegar before meals or as salad dressing with olive oil-supresses appetite
-eating every 2- 3hrs helps keep blood sugar levels stable and you don;t end up binging-trust me