Q & A: An Anorexic Patient Driven to Exercise

Q. I know it is not unusual for patients with anorexia nervosa to use exercise to maintain and increase their weight

loss. However, one of my patients, a 22-year-old college student, seems particularly obsessed with exercising. Has any new research looked into this problem? (DB, Portland)

A. The problem of excessive exercise in these patients is always a perplexing and challenging problem. Several recent studies have investigated an underlying drive for activity (DFA) or driven exercise (DE) that may underlie hyperactivity and increased physical activity.

Dr. L. Sternheim and colleagues at Altrech Eating Disorders Rintveld, The Netherlands, investigated DFA levels in 240 female patients with AN to see if there was any relation between DFA and severity of the disease (In J Eat Disord. 2014 Mar 29. Doi:10.10002/eat.22272[Epub ahead of print]. They also looked at the effects of one aspect of negative affect (anxiety) on DFA rates. Higher DFA was correlated with EDE scores and with anxiety. The authors believe that the results suggest DFA could be considered a core feature in AN.

In a second study, Drs. C. Stiles-Shields and researchers at Northwestern University’s Feinberg School of Medicine and The University of Chicago examined DE in adolescents with bulimia nervosa (BN) and AN (Int J Eat Disord. 2014 Apr 11. doi: 10.1002/eat.22281 [Epub ahead of print].

The study group included 201 teens with eating disorders (80 with BN and 121 with AN) who were being treated at two outpatient specialty clinics. Levels of DE were measured at baseline and correlated with the outcome of treatment.

DE was common (66.3% of adolescents with BN and 23.1% of adolescents with AN). DE predicted worse outcomes for AN but not BN. Thus, DE appears to be common among adolescents with eating disorders and may influence outcomes in those with AN.

One challenge in treating people with driven exercise and AN is anticipating their true energy needs. It is well known that restriction can suppress resting energy expenditure. Does driven exercise significantly increase energy expenditure (and thus caloric needs for weight restoration)? Zipfel and colleagues (Lancet. 2014; 3843: 217) suggest that high levels of exercise do significantly increase total daily energy expenditure.

The authors suggest that clinicians assess the amount of exercise with a single question from the Eating Disorder Inventory: “What percentage of your exercise is aimed at controlling your weight?”

— SC