Yes some chemicals are very bad in some doses. The diet pills that were taken off the market were doing the job they were meant to do but people kept taking them until they reached a lethal dose. Now it is true that shivering can help you lose weight too. The body's natural reaction to lower temps is to increase metabolism to increase warmth in the body. Shivering has always been a sign that your body is cold and it helps to increase the temperature in the human body. This is all old science.