Fitness trackers: What’s the value in numbers?

    Fitness trackers are incredibly popular, but there is limited empirical evidence that they can lead to long-term health outcomes.

    Although the smartwatch market may be on the decline, a recent report indicates that overall wearables are still experiencing steady growth (IDC, 2016). Much of this increase is thanks to fitness trackers, such as those offered by Fitbit (Llamas, 2016). It is not hard to see why fitness trackers are appealing. Precise data about our lifestyle should highlight bad habits and mark our progress towards self-improvement goals. However, a number of recent findings call into question the efficacy of such devices. In this article, I want to discuss the evidence (or lack thereof) for fitness tracker effectiveness.

    Fitness trackers versus standard interventions

    In a recent large-scale study of 471 overweight students (body-mass-index of 25-40), researchers investigated the effectiveness of wearable technologies over standard weight loss interventions (Jakicic et al., 2016). Participants began with a low-calorie diet, physical exercise, and group counseling sessions. After a period of six months, the researchers then randomized participants into one of two conditions. In the standard condition, participants self-monitored their behavior by entering their exercise and diet data on a custom website. In the wearable condition, participants used a fitness tracker to monitor their performance, which synchronized with an online interface.

    Checking in a year later, the researchers found that both groups had indeed lost weight. However, the standard intervention group had lost an average of 5.9 kilos whereas the wearable group had lost only 3.5 kilos. Perhaps most interestingly, diet and exercise could not explain the outcome: both groups reported similar (and not statistically different) improvements in diet and exercise. Although it remains ambiguous why the wearable users lost less weight, the findings led the authors to question the use of such technologies for the purposes of weight loss.

    Fitness trackers with incentives

    Another large study conducted in Singapore yielded similar results (Finkelstein et al., 2016). Researchers sorted 800 employees from 13 organizations into one of four conditions, receiving either only a fitness tracker, a fitness tracker and financial incentives, a fitness tracker and charity incentives, or nothing (control condition). Again, the researchers found that the fitness tracker was associated with increased exercise. After a year (but not at 6 months), the fitness tracker (with or without charity incentives) was more effective than the control group at promoting exercise. The group given only a fitness tracker logged an additional 37 minutes per week more exercise than those without. However, none of the groups given a fitness tracker exhibited significant improvements in health outcomes.

    Let’s recap these results. In the first experiment, although the fitness trackers were associated with improvements in diet and exercise, the users lost less weight than those with a standard intervention. In the second experiment, the fitness trackers were again associated with moderately higher levels of exercise but also yielded no benefits to health outcomes. This begs the question: why are fitness trackers increasing levels of exercise while yielding little in the way of long-term benefits? From these studies alone, it is difficult to answer such a question. However, recent research featured in the Journal of Consumer Research may shine some light on the phenomenon.

    How do numbers affect our motivation?

    Jordan Etkin from Duke University examined the effects of quantifying enjoyable activities (2016). Etkin drew upon the theory that motivation can be intrinsic, where the behavior is enjoyable for its own sake, and extrinsic, where rewards and punishment drive behavior. Moreover, she proposed that measuring an activity shifts focus from fun (intrinsic) to output (extrinsic). Accordingly, she ran a series of studies where she asked participants to color simple shapes, take a walk, or read an excerpt from a book. In each experiment, some participants had access to measurement information. For example, Etkin told them how many shapes they colored, how many steps they took, or how much they read. The remaining participants had no access to such information.

    The experiments revealed an interesting discrepancy: although measurement generally increased output, participants reported enjoying the activities significantly less. Moreover, the output increase only lasted as long as the measurement was available. When participants who had previously used the tracking information no longer had access to it, their performance decreased relative to the control group. The reason for this? In some of the experiments, Etkin also asked participants their perception of the activity, and this revealed that when participants had access to such metrics, the activities felt less like leisure and more like work.

    To track or not to track

    These findings have important implications for consumers looking to track their resolutions with quantifiable data: doing so with activities that are already pleasurable may, in fact, ruin them altogether. Paired with the two studies on weight loss described previously, they also suggest that motivation may be partially responsible. By turning what can be an intrinsically rewarding activity into a chore, participants may have not have applied the same level of enthusiasm as participants who were not tracked as closely (i.e. only self-reporting performance or nothing at all). Of course, such an explanation is speculative, and further research is necessary. Nevertheless, it seems clear that effective behavioral change requires more than access to simple exercise metrics.

    The point of this article is not to completely dismiss fitness tracking and the quantified-self. All three studies demonstrated some degree of behavioral change, even if the fitness trackers were rarely associated with long-term benefits. Another point of note is that the participants in these studies are not necessarily the standard user. The results might be quite different if the researchers were to study those who voluntarily purchase and use such a device. People committed to their exercise goals to such a degree that they buy a fitness tracker may benefit far more from the device than those who have it thrust upon them in a large impersonal longitudinal study. Nevertheless, the research highlights the limitations of these devices. They are clearly better suited to activities that people already find to be a chore, and may not be much more effective than standard weight loss interventions.


    Etkin, J. (2016). The hidden cost of personal quantification. Journal of Consumer Research, 42(6), 967-984.

    Finkelstein, E. A., Haaland, B. A., Bilger, M., Sahasranaman, A., Sloan, R. A., Nang, E. E. K., & Evenson, K. R. (2016). Effectiveness of activity trackers with and without incentives to increase physical activity (TRIPPA): a randomised controlled trial. The Lancet Diabetes & Endocrinology, 4(12), 983-995.

    Jakicic, J. M., Davis, K. K., Rogers, R. J., King, W. C., Marcus, M. D., Helsel, D., … & Belle, S. H. (2016). Effect of wearable technology combined with a lifestyle intervention on long-term weight loss: the IDEA randomized clinical trial. Jama, 316(11), 1161-1171.

    Llamas, R. (2016, December). Fitness Trackers in the Lead as Wearables Market Grows 3.1% in the Third Quarter, According to IDC. Retrieved from


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