The aims of this paper were to compare (1) the proportion of participants diagnosed with threshold or subthreshold Bulimia Nervosa (BN) and Binge Eating Disorder (BED) (clinical utility), and (2) the severity of participants' clinical features and mental Health-Related Quality of Life (HRQoL) (convergent validity), when diagnosed according to either the Diagnostic and Statistical Manual of Mental Disorders-5th edition (DSM-5) or the proposed International Classification of Diseases 11th edition (ICD-11) schemes. One hundred and seven adult men and women, with a high Body Mass Index (BMI) were evaluated by interview to confirm their eating disorder diagnoses. All participants completed self-report assessments of current symptoms and mental HRQoL. The majority of participants in either diagnostic scheme were included in the main categories of BN or BED (102/107, 95% in the ICD-11 and 85/107, 79% in the DSM-5). Fewer individuals received a subthreshold other or unspecified diagnosis with the ICD-11 compared to the DSM-5 scheme (5% vs. 21%). No significant differences in demographic, clinical features or mental HRQoL of participants with complete or partial BN or BED were found between diagnostic categories. Compared to the DSM-5, the proposed ICD-11 was not over inclusive, i.e., it did not appear to include people with less severe and potentially less clinically relevant symptoms. These results support the greater clinical utility of the ICD-11 whilst both schemes showed convergent validity.