Key messages
- The results we identified are insufficient to show that smartphone apps help teenagers and adults with overweight or obesity. When we compared smartphone apps to doing nothing or personal coaching, the differences we found were small and might not have an important impact on everyday life.
- We do not have much information about teenagers. We also do not know how well smartphone apps work in different countries, or for people who have less money or different backgrounds.
- Thirty-four studies on this topic are ongoing, and we expect to learn more within the next two years.
- Doctors and other health professionals need to think carefully about whether to recommend smartphone apps to people with overweight or obesity.
What are overweight and obesity?
Being overweight means weighing more than what is considered usual for a person's height. This is often expressed using the body mass index (BMI, which is a person's weight in kilograms divided by the square of their height in meters (kg/m²)). For adults with overweight, this means having a BMI of 25 to 30. Obesity is when someone is significantly overweight and has a higher risk for health problems. For adults, this means having a BMI of over 30. Besides possible health problems, people with obesity are often treated unfairly by those around them.
What are smartphone apps for people with overweight and obesity?
Smartphone apps are programs that run on a smartphone. They can help people with overweight and obesity to make good health choices in their lives. They might encourage teenagers and adults to become more physically active, change how they eat, or think more positively about themselves. These apps are thought to help people stay on track with healthy habits.
What did we want to find out?
We wanted to study whether using smartphone apps was helpful for adults (people aged over 18 years), and teenagers (people aged 13 to 17 years) with overweight or obesity.
What did we do?
We looked for studies that randomly assigned people to receive either a smartphone app, another treatment, or usual care (called 'interventions'). The studies help us to find out if smartphone apps are effective and if they are better than another intervention. We chose studies that included teenagers or adults with overweight or obesity and tested a smartphone app as a single intervention. To be included, the app needed to support people by using at least two 'behaviour change techniques'. This means that the app had to help people to, for example, track their weight, food or activity and additionally provide, for example, motivational messages or information about healthy habits. We focused on the results of the studies at six months or longer (medium-term) and 12 months or longer (long-term).
What did we find?
We included eighteen studies with 2703 people. Sixteen studies included adults and two included teenagers. The interventions in the studies lasted between 2 and 24 months. We also found 34 ongoing studies on this topic, which could add data in a future update of our review.
Smartphone app compared with no app
Thirteen studies compared adults with a smartphone app against those without an app. A smartphone app probably reduces moderate to vigorous physical activity, and leisure activities probably do not change. A smartphone app may reduce BMI in the medium-term, but the evidence is very uncertain. There was probably little or no change in weight two years after the start of the study. A smartphone app probably results in little to no difference in quality of life and well-being after one year and in little to no difference in dietary habits after one or two years. We found no studies in teenagers.
Smartphone app compared with another smartphone app
Two studies compared adults with different versions of the same app and showed no or minimal differences in results. A third study in adults compared two different apps (counting calories or using a ketogenic diet) and suggested a slight decrease in weight at six months with the ketogenic diet. We found no studies in teenagers.
Smartphone app compared with personal coaching
One study compared adults with a smartphone app against those who had personal coaching. It reported only short-term results. Two studies compared an app against personal coaching in teenagers. One of them showed that a smartphone app resulted in little to no difference in BMI compared to personal coaching after six months.
Smartphone app compared with usual care
Only one study compared an app with usual care in adults but only reported short-term results. We found no studies in teenagers.
What are the limitations of the evidence?
In general, we are moderately to very uncertain about the effects of smartphone apps. The results of the comparisons showed wide variations that were not clearly in favour of smartphone apps. Many studies only had a few participating people and short observation periods.
How up-to-date is this review?
This evidence is up-to-date as of 2 October 2023.
The available evidence is limited and does not demonstrate a clear benefit of smartphone applications as interventions for adolescents or adults with overweight or obesity. While the number of studies is growing, the evidence remains incomplete due to the high variability of the apps' features, content and components, which complicates direct comparisons and assessment of their effectiveness. Comparisons with either no or minimal intervention or personal coaching show minor effects, which are mostly not clinically significant. Minimal data for adolescents also warrants further research. Evidence is also scarce for low- and middle-income countries as well as for people with different socio-economic and cultural backgrounds. The 34 ongoing studies suggest sustained interest in the topic, with new evidence expected to emerge within the next two years. In practice, clinicians and healthcare practitioners should carefully consider the potential benefits, limitations, and evolving research when recommending smartphone apps to adolescents and adults with overweight or obesity.
Obesity is considered to be a risk factor for various diseases, and its incidence has tripled worldwide since 1975. In addition to potentially being at risk for adverse health outcomes, people with overweight or obesity are often stigmatised. Behaviour change interventions are increasingly delivered as mobile health (m-health) interventions, using smartphone apps and wearables. They are believed to support healthy behaviours at the individual level in a low-threshold manner.
To assess the effects of integrated smartphone applications for adolescents and adults with overweight or obesity.
We searched CENTRAL, MEDLINE, PsycINFO, CINAHL, and LILACS, as well as the trials registers ClinicalTrials.gov and World Health Organization International Clinical Trials Registry Platform on 2 October 2023 (date of last search for all databases). We placed no restrictions on the language of publication.
Participants were adolescents and adults with overweight or obesity. Eligible interventions were integrated smartphone apps using at least two behaviour change techniques. The intervention could target physical activity, cardiorespiratory fitness, weight loss, healthy diet, or self-efficacy. Comparators included no or minimal intervention (NMI), a different smartphone app, personal coaching, or usual care. Eligible studies were randomised controlled trials of any duration with a follow-up of at least three months.
We used standard Cochrane methodology and the RoB 2 tool. Important outcomes were physical activity, body mass index (BMI) and weight, health-related quality of life, self-efficacy, well-being, change in dietary behaviour, and adverse events. We focused on presenting studies with medium- (6 to < 12 months) and long-term (≥ 12 months) outcomes in our summary of findings table, following recommendations in the core outcome set for behavioural weight management interventions.
We included 18 studies with 2703 participants. Interventions lasted from 2 to 24 months. The mean BMI in adults ranged from 27 to 50, and the median BMI z-score in adolescents ranged from 2.2 to 2.5.
Smartphone app versus no or minimal intervention
Thirteen studies compared a smartphone app versus NMI in adults; no studies were available for adolescents. The comparator comprised minimal health advice, handouts, food diaries, smartphone apps unrelated to weight loss, and waiting list.
Measures of physical activity: at 12 months' follow-up, a smartphone app compared to NMI probably reduces moderate to vigorous physical activity (MVPA) slightly (mean difference (MD) −28.9 min/week (95% confidence interval (CI) −85.9 to 28; 1 study, 650 participants; moderate-certainty evidence)). We are very uncertain about the results of estimated energy expenditure and cardiorespiratory fitness at eight months' follow-up. A smartphone app compared with NMI probably results in little to no difference in changes in total activity time at 12 months' follow-up and leisure time physical activity at 24 months' follow-up.
Anthropometric measures: a smartphone app compared with NMI may reduce BMI (MD of BMI change −2.6 kg/m2, 95% CI −6 to 0.8; 2 studies, 146 participants; very low-certainty evidence) at six to eight months' follow-up, but the evidence is very uncertain. At 12 months' follow-up, a smartphone app probably resulted in little to no difference in BMI change (MD −0.1 kg/m2, 95% CI −0.4 to 0.3; 1 study; 650 participants; moderate-certainty evidence). A smartphone app compared with NMI may result in little to no difference in body weight change (MD −2.5 kg, 95% CI −6.8 to 1.7; 3 studies, 1044 participants; low-certainty evidence) at 12 months' follow-up. At 24 months' follow-up, a smartphone app probably resulted in little to no difference in body weight change (MD 0.7 kg, 95% CI −1.2 to 2.6; 1 study, 245 participants; moderate-certainty evidence).
A smartphone app compared with NMI may result in little to no difference in self-efficacy for a physical activity score at eight months' follow-up, but the results are very uncertain. A smartphone app probably results in little to no difference in quality of life and well-being at 12 months (moderate-certainty evidence) and in little to no difference in various measures used to inform dietary behaviour at 12 and 24 months' follow-up.
We are very uncertain about adverse events, which were only reported narratively in two studies (very low-certainty evidence).
Smartphone app versus another smartphone app
Two studies compared different versions of the same app in adults, showing no or minimal differences in outcomes. One study in adults compared two different apps (calorie counting versus ketogenic diet) and suggested a slight reduction in body weight at six months in favour of the ketogenic diet app. No studies were available for adolescents.
Smartphone app versus personal coaching
Only one study compared a smartphone app with personal coaching in adults, presenting data at three months. Two studies compared these interventions in adolescents. A smartphone app resulted in little to no difference in BMI z-score compared to personal coaching at six months' follow‐up (MD 0, 95% CI −0.2 to 0.2; 1 study; 107 participants).
Smartphone app versus usual care
Only one study compared an app with usual care in adults but only reported data at three months on participant satisfaction. No studies were available for adolescents.
We identified 34 ongoing studies.