Objective The recent DSM-5 categorization of eating disorders introduces a new category of eating disorders, Unspecified Feeding and Eating Disorders (UFED), where symptoms do not meet criteria for any other diagnostic category, but cause clinically significant distress or impairment. The aim of the current study was to explore what disorders in UFED might look like in an adolescent population. Method We examined a large cohort of adolescent female twins (N = 699) who were assessed on three occasions and who did not meet a DSM-5 eating disorder diagnosis but who reported threshold levels of either fasting and/or driven exercise (N = 33; 4.7%). This group of girls was compared to girls who reported no eating disorder over the three waves, and girls who met a diagnosis of either anorexia nervosa (AN) or atypical AN. Results The UFED group was characterized as being in the overweight range while striving to lose weight, and placing a high degree of importance on weight and shape in their self-evaluation. This group was indistinguishable from the two eating disorder groups on measures of global eating disorder severity, and demonstrated significantly elevated impairment and distress compared to the no eating disorder group commensurate with the eating disorder groups. Discussion Further research of this group is necessary to ensure that these individuals are not overlooked, and that treatment options are appropriate and available.