Physical activity (PA) in the context of eating disorders (EDs) can be either maladaptive (i.e., used to compensate for binge eating or feels driven to avoid negative consequences of not exercising such as weight gain) or adaptive (i.e., neither driven, nor compensatory). The inclusion of fitness trackers in research studies may be a useful methodology in understanding objective characteristics of PA in EDs (e.g., duration, frequency, intensity), but such methods are underutilized in research studies to-date due to concerns about participant reactivity to trackers. The current study aims to improve understanding of the perceived impact of fitness trackers on ED symptoms and PA engagement in an ED population in order to evaluate safety and potential efficacy of use for research studies.
Use of Fitness Trackers in Extant Research
There is a growing literature base examining PA in the context of eating disorders EDs. To date, most research on PA in ED populations has relied on retrospective self-report measures of PA frequency and duration (Bezzina et al., 2019). These retrospective self-report measures are subject to several biases, such as recall bias (e.g. forgetting ) and social desirability bias (e.g. over/underreporting) (Bezzina et al., 2019). Other literature has used ecological momentary assessment (EMA) to examine PA in EDs. While EMA reporting reduces recall errors, it is still subject to social desirability bias. Extant literature supports these concerns; self-report measurements of PA have been found to be inaccurate both in ED groups and in the general adult population (Bezzina et al., 2019; Mathisen et al., 2018; Prince et al., 2008).
Objective measurement of PA via sensors (e.g., accelerometry) shows great promise for more accurate measurement of PA engagement in ED populations. Sensor-based assessment tools (e.g., wearable fitness trackers) use objective measurement, more accurately measure the amount of PA, and increase the credibility and validity of research findings (Grosser et al., 2020; Mathisen et al., 2018). Despite these strong benefits of objective PA measurement, few studies have objectively measured the amount of PA cross sectionally (Carr, Lydecker, White, & Grilo, 2019; Mathisen et al., 2018). There are two main reasons why the ED field tends to under-use objective measures of PA in research assessment. First, many characteristics of both maladaptive and adaptive exercise are cognitive in nature, and prior research suggests these cognitive components of exercise are more clinically relevant in defining maladaptive exercise as compared to exercise frequency and duration (Coniglio, Davis, Sun, Loureiro, & Selby, 2021). For example, wearable fitness trackers cannot measure a sense of being compelled or driven to continue exercise or the intended reason for exercise. As a result, researchers cannot presently depend on wearable fitness trackers to distinguish adaptive from maladaptive exercise, though they can use these devices to gain objective data about other important exercise features such as duration and intensity. Second, researchers and clinicians are often concerned about the potential negative effects wearable fitness trackers could have on the development and maintenance of ED symptoms (Simpson & Mazzeo, 2017). Thus, the use of fitness trackers in ED research has remained limited.
Despite concerns about reactivity to sensor measurement of PA among individuals with EDs, little research has specifically examined this phenomenon. To date, only three studies have tested the effects of a wearable fitness trackers on ED symptoms in non-clinical populations, with mixed results. Two were observational studies of university students or young adults which found fitness tracker devices and apps (e.g., Fitbit) were associated with ED symptomatology (e.g., rates of binge eating or purging) and higher rates of body dissatisfaction (Honary, Bell, Clinch, Wild, & McNaney, 2019; Simpson & Mazzeo, 2017). The third study assigned half their sample of university students to wear fitness trackers and found those that were assigned to wear fitness trackers were more likely to report exercising to support their health and fitness and were less likely to report engagement in ED behaviors (e.g., dietary restraint, binge eating) (Gittus et al., 2020). A major limitation of all the studies described above is that none of them included individuals with a diagnosed ED. Despite the valuable contributions of the aforementioned studies, it remains unknown how using wearable fitness trackers impacts individuals with EDs, specifically.
Patient Perceptions of Influence of Fitness Trackers on ED Behaviors
In addition to the field’s limited understanding of the relationship between wearable fitness trackers, ED symptoms, and PA engagement, no study has assessed the perceived impact of fitness trackers on ED symptoms and PA engagement over an extended period (e.g., >10 days), nor throughout the course of an ED treatment. Importantly, there could be increased reactivity during the first few days of wear as compared to longer-term wear of fitness trackers. Assessing the perceived impact of a fitness tracker on PA engagement and ED symptoms during an ED treatment will allow for the opportunity to further understand the perceived impact of the fitness tracker at the start of treatment when ED symptoms are likely more severe or during treatment when ED symptoms are likely subsiding.
Influence of Maladaptive Exercise on Fitness Tracker Reactivity
To date, research has also not assessed the perceived influence of fitness trackers on PA engagement and ED symptoms separately in individuals with EDs that do and do not engage in maladaptive exercise. It is possible the perceived impact of fitness trackers may be different among those with and without maladaptive exercise as these groups tend to show different symptom presentations prior to treatment (Levallius, Collin, & Birgegård, 2017; Shroff et al., 2006; Welch, Birgegård, Parling, & Ghaderi, 2011). Assessing the perceived impact of fitness trackers on PA engagement and ED symptoms during an ED treatment may reveal whether specific ED symptoms, like maladaptive exercise, predict whether an individual perceives the fitness tracker to positively or negatively impact their ED symptoms and/or PA engagement.
Current Study
The current study aimed to characterize participants’ perception of the fitness tracker's influence on ED symptoms across a 12-week CBT treatment for individuals with an ED characterized by both clinically significant binge eating and restrictive eating. There were two aims of the current study and each aim consisted of two parts. Aim 1a was to describe session-by-session perception of the fitness trackers influence on overall PA and maladaptive PA among individuals who did and did not engage in maladaptive exercise at pre-treatment. For Aim 1b, we aimed to examine the moderating role of pre-treatment maladaptive exercise engagement on the perceived influence of the fitness tracker on overall PA engagement across treatment. Due to the potentially greater perceived impact of fitness trackers on PA engagement among individuals currently engaging in maladaptive exercise, we hypothesized the individuals that entered treatment engaging in maladaptive exercise would experience greater reductions of the perceived influence of the fitness tracker on PA engagement during treatment compared to those that did not engage in maladaptive exercise at the start of treatment. Aim 2a was to characterize session-by-session perception of the fitness trackers influence on ED symptoms among individuals who did and did not engage in maladaptive exercise at pre-treatment. For Aim 2b, we aimed to examine the moderating role of pre-treatment maladaptive exercise engagement on the perceived influence of the fitness tracker on ED symptoms across treatment. We had no specific directional hypotheses for whether the perceived influence of the fitness tracker on ED symptoms would differ throughout the course of treatment between those that did and did not engage in maladaptive exercise at the start of treatment.