The prevalence of obesity among adults in the United Kingdom increased from 14.9% in 1993 to 25.6% in 2014 [
1]. To help people lose weight, interventionists within the National Health Service (NHS) can encourage them to change their lifestyle, provide them with medications, and, if suitable, provide them with bariatric surgery [
2]. Bariatric surgery is currently the most effective long-term treatment for severe obesity (particularly in the presence of Type 2 diabetes). However, its cost-efficacy for uncomplicated obesity is debated [
3], and even after receiving bariatric surgery 10 to 20% of patients still experience suboptimal long-term weight loss [
4,
5]. The long-term success of bariatric surgery depends in part on patients’ adherence to physical activity recommendations [
6‐
9], and many patients likely require additional support to follow through on their good intentions. The current article seeks to evaluate the feasibility of using smartphone apps to track such patients’ physical activity and other health-related variables.
Physical activity
Public health guidelines from the United States and United Kingdom recommend that adults engage in at least 150 min per week of moderate-to-vigorous physical activity (MVPA) and minimise sedentary behaviour to enhance health-related outcomes [
10]. These guidelines extend to patients with chronic conditions or disabilities where they are able to engage. After undergoing bariatric surgery patients are encouraged to engage in MVPA for at least 10-min bouts every day [
11,
12]. A 2016 review of 50 studies measuring such patients’ physical activity suggests that many patients do increase their physical activity post-bariatric surgery [
13]. However, only 7 of the 50 studies included objective measures of physical activity, so the inference that these patients’ physical activity increased largely relies on self-reports that may be affected by response biases, e.g. social desirability. A further concern is that of these seven studies only one assessed patients’ MVPA [
14]. This study suggests that 89% of patients do not engage in the recommended MVPA in at least 10-min bouts every day. So even patients who increase their physical activity may still not be engaging for sufficient durations and or at sufficient intensities to gain the optimal benefit. Whilst historically tracking physical activity in real-time has been difficult, newer activity-monitoring tools are increasingly capable.
Monitoring physical activity using technology
Whilst offering patients support to increase their physical activity is encouraged by NHS England’s Obesity Clinical Reference Group guidelines, such support is often lacking in part because practitioners do not know how active patients are [
15]. Providing patients with activity-monitoring tools could help practitioners offer support in a data-led fashion. This possibility encourages the development of technologies that can obtain richer and more objective physical activity profiles, such as smartphone applications (hereafter referred to as ‘apps’). Pew Research Centre’s (2019) research suggests that 76% of the UK adults currently own a smartphone [
16], and a number of apps already exists that allow users to track their daily physical activity and create physical activity profiles. A number of recent studies have already used apps to track weight loss [
17‐
19]. Ross and Wing’s study included an analysis of 68 million days of physical activity for over 700,000 people worldwide, and found that people who were less active were more likely to be obese [
20].
A reliable app that tracks physical activity could eventually be used to deliver timely interventions to patients. These apps should be ergonomically designed and motivate users to be more active. For example, patients who do not engage in sufficient activity for multiple days could be sent a text-message that motivates them to move more or to schedule an appointment. The apps may even help patients motivate themselves by prompting them to set daily, weekly, and monthly targets, as well as by sending them automated reminders to engage in exercise based on their self-set goals. For example, a motivating personalised message might say, “[Name], you are almost there, an 8 minute brisk walk will allow you to achieve your move goal today”.
From a research perspective, the importance of developing mobile health (i.e. mHealth) technologies that are user-friendly and easily accessible is important in order to encourage participants to record their data. From a practice perspective, reliable apps that track and motivate patients physical activity could help practitioners increase what are typically poor following-up rates with patients after they have had bariatric surgery [
21]. Many patients miss in-person follow-up appointments for various reasons, such as the distance they need to travel or their ability to get time off work [
22]. Enabling these patients to attend their follow-up appointment remotely, informed by their own physical activity data, may be sufficient to increase the long-term success rates of bariatric surgery [
23‐
25]. There are already many apps for patients’ with chronic health conditions and many users have positive reactions to them, e.g. they experience an increased sense of agency [
26]. Thomas et al. argue that these technologies are not only cost-effective but are also ecological valid feedback tools [
27]. As highlighted by Bradley et al.’s review, it appears that patients are receptive to remote assessment [
28]. Despite these advancements in app technologies, the feasibility of remotely monitoring patients’ health-related data via apps is largely unexplored, few studies address evidence-based physical activity guidelines, and there is greater scope for these apps to deliver theoretically informed and empirically supported behaviour change techniques [
29].
The current study
The current study aims to evaluate the feasibility of smartphone apps to monitor patients’ physical activity pre- and post-bariatric surgery. Whilst physical activity is the core focus of the current study, other health-related data were also considered, including weight, mood, wakefulness, and satisfaction. These are important health-related variables that impact on physical activity [
26,
30‐
32] and considering them here may help inform the development of future apps. Notably, the reliability of apps depends on more than the technology itself. Specifically, the apps’ reliability also depends on patients using the technology appropriately, e.g. having their phone switched on and kept on their person. To capture this aspect of the apps’ reliability several participants in our study also completed surveys informed by the Theoretical Domains Framework (TDF). The TDF captures the behavioural facilitators and barriers per theoretically and empirically informed behaviour change domains [
33]. The information gathered in the current TDF survey can be used to identify common barriers that future apps should overcome to improve their usability.