Can weight loss cause you not to have a period?

Yes: Weight loss in a woman who is not overweight might drop her body fat below the level needed to have normal menstrual cycles and cause a missed period. Very importantly, a common cause of a missed period is a pregnancy, so a woman who misses a period should do a urine pregnancy test. Sometimes, a hormonal disorder or other illness can cause both weight loss and a missed period.

Yes: Weight loss causes amenorrhea - no period.