Although the percentage of “thin” young women has been increasing in recent years, there are those who are trying to lose even more weight. Such unnecessary weight reduction, which increases health risks, is becoming a problem. This study examines the problem in respect of the eating behavior and fitness habits among female university students that are derived from a desire for thinness and reveals the fashion sense that is a major motivating factor. A questionnaire survey was conducted on 359 female students involving their self-assessment of body type, interest in fashion, experience of weight reduction, attitude regarding eating, and number of meals per day. The results of this study suggest that the concept of “thinness” in women, who appear daily in the media as the models for fashionable dressing, began in childhood. It is this desire for thinness that is adversely affecting adequate nutrition due to unsuitable dietary control and exercise habits, becoming a factor that invites eating disorders and damages the physical and mental health of young women who do not need to lose weight.