Diet pills are very tempting things if you want to lose weight, especially if you have tried several conventional weight loss diets without success. Diet pills are divided into two types prescription-only diet pills and over-the-counter (otc) diet pills. Prescription Diet Pills. These pills are diet drugs. These pills are regulated by the Food and Drug Administration agency (FDA), their side effects are monitored and they may be prescribed. This version is the first release on CNET Download.com.