Premorbid BMIs May Affect ED Diagnosis among Teens


Higher body mass index may be misleading.


Reprinted from Eating Disorders Review
July/August Volume 27, Number 4
©2016 iaedp

Obesity and overweight can affect the presentation of teens with eating disorders. Adolescents with restrictive eating disorders and a high premorbid body mass index (BMI, kg/m2) are less lean when they seek treatment, despite the fact that they may have lost more weight than leaner patients, according to the results of a recent study in Sweden.

Dr. Ingemar Swenne of Uppsala University, Sweden, concluded this after studying the effect of premorbid BMIs on clinical characteristics of teenage girls entering eating disorder treatment (BMC Psychiatry. 2016; 16:81). Overweight teens may have had ED symptoms for a long time but still presented with higher BMIs than those who had premorbid weight in a normal range. Despite marked weight loss, these teens may still not reach weight criterion for anorexia nervosa (AN), for example, and thus are often placed in the eating disorder not otherwise specified (EDNOS) category.

Dr. Swenne analyzed data from 275 postmenarcheal girls being treated for an eating disorder for the first time. Recorded premorbid maximal weights were obtained, and prepubertal weights measured at about 7 years of age were available for 80% of the girls. Two self-report questionnaires, the Eating Disorders Examination-Questionnaire, youth edition (EDE-Q), and the Montgomery-Åsberg Depression Rating Scale-self-report (MADRS) were administered. Study participants had BMI scores recalculated into BMI standard deviation scores (BMI SDS), to correct this for age, as this was an adolescent sample. EDE-Q global scores and EDE-Q restraint, shape concern, and weight concern subscale scores and MADRS were no less severe in the higher-BMI groups.

Speed of weight loss is a diagnostic consideration

Most of the patients had a premorbid BMI SDS above the population average, and teens with restrictive eating disorders and a high premorbid BMI were less lean when they presented for treatment, despite having lost more weight. The important point, according to Dr. Swenne, is that such patients can nevertheless have the same level of eating disorder cognition as more emaciated patients and also have signs and laboratory findings that indicate starvation despite being at near-normal weights.

Signs of starvation such as low blood pressure and a low heart rate are related to low weight, and are often used as signals for needed interventions and hospitalization. The severity of these signs depends not only on low weight/BMI but on the individual patient’s degree and speed of weight loss. Eating disorder cognitions and extreme weight control behaviors may have been present in the girls in the highest premorbid BMI SDS class even before the point at which their eating disorders were thought to have begun.

The study results fit well with extensive prior work that has shown that “subthreshold” EDs that fall under EDNOS are no less severe than “full” EDs. They serve as a reminder that this group is one where case finding may fall short. As such, it is important to consider the possibility of an eating disorder when an overweight teen loses weight rapidly.

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