In short, yes, most diet pills are bad for you. Even though some might not be harmful, supplements and over-the-counter (OTC) weight-loss remedies that tout a quick fix usually don't work — if it sounds too good to be true, it probably is.
Many OTC diet pills are intended for obese adults and are not recommended for anyone under 18. Among the many reasons why diet pills aren't a good idea are the unpleasant side effects, which include gas (farting), oily discharge, and diarrhea — just to name a few.
On the other end of the diet-pill spectrum are herbs and supplements. What separates these diet pills from the rest is that they are not regulated by the U.S. Food and Drug Administration (FDA) and are not held to the same standards as prescription and OTC medicines. These products may claim you can shed pounds without diet or exercise, but the bottom line is that their effectiveness is questionable at best, and side effects can be as serious as those seen with prescription and OTC drugs, ranging from bloating and diarrhea to serious heart problems.
If you think you're overweight, talk to your doctor about safe and effective ways to lose weight. The best way to attack a weight problem is through lifestyle changes like choosing healthy foods, eating smaller portions, and getting off the couch and starting an exercise routine.