Fitness trackers added 1656 steps a day, mostly for older White men

Wearable activity trackers are now widely recommended for people with conditions such as diabetes, obesity and cardiovascular disease, and existing evidence supports their use. Yet the health benefits measured in trials have been small and muddied by differences between studies, which leaves a practical question unanswered: who actually benefits? An average effect can hide big differences between groups, and the only way to see those differences is to analyse the underlying data person by person. That is what this study set out to do, pooling raw participant data from multiple trials rather than relying on their published summaries.

The researchers requested individual participant data from randomised trials of wearable trackers run before December 2020, all measuring steps per day as the primary outcome in adults with cardiometabolic conditions including diabetes, overweight or obesity, and cardiovascular disease. They obtained data from 9 of 25 eligible trials, covering 1481 of 3178 total participants, or 47%. Statistical models accounted for the clustering of participants within trials and for differences across trials, producing overall estimates plus subgroup comparisons by sex, age, ethnicity and number of other health conditions.

Over a median intervention length of 12 weeks, wearable tracker interventions increased activity by 1656 steps per day, a significant change. The gains were not evenly spread: men improved more than women, every age band above 50 improved more than those under 50, White participants improved more than non-White participants, and people with fewer other health conditions improved more than those managing several. Among the features of the interventions themselves, only face-to-face delivery of the tracker made a difference to effectiveness. The authors' blunt conclusion was that these interventions mostly benefited older White men without multimorbidity.

The headline finding, that trackers genuinely increase daily activity in people with cardiometabolic conditions, fits comfortably with the existing evidence. What this analysis adds is the uncomfortable detail underneath the average: the benefit concentrates in specific groups, and women, younger adults, non-White participants and people with multiple conditions gained less. Why that is remains an open question, as does whether differently designed interventions could close the gap. It also matters that only 9 of the 25 eligible trials shared their data, so the picture could shift as more datasets become available.

If you have a cardiometabolic condition and are considering a tracker, this is decent evidence that one can meaningfully raise your daily step count, at least over roughly 12 weeks. It is also a reminder that averages are not promises: the boost was clearly larger for some groups than others. The finding that face-to-face delivery mattered hints that the device alone is not the whole story. For anyone outside the groups that benefited most, the honest reading is that the evidence is thinner, not that a tracker will not help.