Weight-loss apps barely shift the scales after a year

Obesity incidence has tripled worldwide since 1975, and smartphone apps promise a cheap, low-threshold way to support weight loss, healthier eating and more activity. Millions of people download them, so it matters whether they actually change outcomes rather than just log them. This review, conducted to rigorous standards, asked whether integrated smartphone apps using at least two behaviour change techniques help adolescents and adults with overweight or obesity, compared against minimal intervention, other apps, personal coaching or usual care.

The authors searched five databases and two trial registries up to 2 October 2023 for randomised controlled trials with at least three months of follow-up. Eighteen studies with 2703 participants were included, with interventions lasting from 2 to 24 months; mean BMI in the adult studies ranged from 27 to 50, and the median BMI z-score in adolescent studies ranged from 2.2 to 2.5. Outcomes included physical activity, BMI and weight, quality of life, self-efficacy, dietary behaviour and adverse events, with the emphasis on results at six months and beyond.

Against no or minimal intervention, an app probably made little to no difference to BMI change at 12 months, and may have made little to no difference to weight change at 12 months across 3 studies with 1044 participants, with the same picture at 24 months in 245 participants. A possible BMI reduction at six to eight months in 2 small studies of 146 people was rated very uncertain. Apps probably slightly reduced moderate to vigorous physical activity at 12 months in one study of 650 people, and quality of life, well-being and dietary behaviour barely differed. Against personal coaching, an app made little to no difference to adolescent BMI z-score at six months.

This is a sobering counterpoint to the enthusiasm around digital health: the pooled evidence does not demonstrate a clear benefit of weight-loss apps for adolescents or adults. The authors stress that apps vary so much in features and components that direct comparison is difficult, and evidence is scarce for adolescents, for low- and middle-income countries and for different socio-economic backgrounds. With 34 ongoing studies identified, the field is active and new evidence is expected within the next two years, so this verdict is a snapshot rather than a full stop.

If an app helps you track food or stay accountable, nothing here says to delete it, but this is a reason not to expect the app itself to produce weight loss. The trials suggest that whatever drives successful weight management, it is not reliably delivered through a smartphone screen alone, at least not by the apps tested so far. Treating an app as a convenient tool rather than an intervention in its own right fits the current evidence best.