Despite being at a dangerously low weight, clinicians have long observed that many people with anorexia nervosa (AN) are very physically active. In fact, when asked about their levels of physical activity, patients with AN report that they are more active than individuals without eating disorders. But, are folks with AN really more physically active than those without an eating disorder, or do clinicians and patients just perceive that the patients are more active? And, what effect does physical activity have on recovery for people with AN? These were the questions that we sought to answer in a recent project and publication: Physical Activity and Post-treatment Weight Trajectory in Anorexia Nervosa.
In this study, we wanted to know:
- Are people with AN more physically active than healthy individuals without eating disorders?
- How does level of physical activity affect how patients with AN do after treatment?
To answer these questions, we collected information from two groups: inpatients with AN (ages 15 to 40), and healthy individuals without an eating disorder. To measure physical activity, participants wore a sophisticated activity monitor, like the one pictured below, attached to their chests, legs, and arms for three consecutive days. Healthy controls wore the activity monitor on one occasion and patients wore it at three different time points: 1) when they were hospitalized and at a low weight, 2) while hospitalized, but restored to normal weight, and 3) one month after discharge from the inpatient program.
Were patients more physically active than healthy controls?
Once patients with AN were back in the “real world”, one month after being discharged from inpatient treatment, they were more physically active during the day and less active at night than healthy controls. The activity monitor used in this study was sophisticated enough that it was able to differentiate several different types of physical activity, from walking to jumping to running to fidgeting. In looking at the breakdown of different types of physical activity, we learned that patients with AN spent significantly more time on their feet (i.e., walking, running, standing, jumping, and stepping up and down stairs) than healthy controls during the day, but less time on their feet at night. Even more specifically, it seemed that time spent standing made the difference between the two groups.
Was physical activity related to treatment outcomes for patients with anorexia nervosa?
The more time patients spent on their feet once they were weight-restored on the inpatient unit, the more rapidly they lost weight in the year after leaving treatment. Other types of physical activity (e.g., fidgeting) were not associated with weight loss after treatment.
Why do these results matter?
While it’s important that these results be replicated before drawing too strong a conclusion, they suggest that helping people with AN learn to minimize physical activity and/or be active in ways that do not compromise their eating disorder recovery would be an important target in treatment.
For example, these results suggest that clinicians should ask their patients about their involvement in a range of physical activity, and not just “exercise” per se. For patients, these results suggest that they could benefit from engaging in self-monitoring of physical activity, asking others for feedback on their level of activity, and challenging themselves to sit down or be still during or after certain activities, like meals or when riding public transportation.