Why do I get strange dreams while fasting?

Lots of people report changes in sleep habits when they start fasting. Most commonly, fasters report sleeping more deeply and having more vivid dreams at night. The effects of fasting on sleep quality and duration have only been studied in two trials to date. Most recently, it was shown that time restricted feeding (limiting the eating window to 10 hours per day, and water fasting the rest of the time) improved sleep quality in overweight men and women. Another study showed that fasting for one week (while consuming 300 calories per day) improved overall sleep quality while boosting daytime concentration. This study also reported mild increases in REM sleep. REM is the sleep stage where we experience our most vivid dreams, so this could explain why some people experience very lucid dreams on fast days.