Technically called polyol, sugar alcohol is neither sugar nor alcohol. Per gram, sugar alcohol has less calories than sugar and it does not require insulin to turn into energy. The most common types of sugar alcohol are sorbitol, maltitol, isomalt, and xylitol (used in sugar-free gum).
And ofcourse, there are side effects of eating too much sugar alcohol. Common problems are gastrointestinal in nature, including bloating and diarrhea. These problems are more pronounced in people who have had gastric-bypass surgery.