Credit: nimito on Shutterstock
That Fitness App May Not Be So Healthy After All, Especially For Teens
In A Nutshell
- A review of 35 studies with an average participant age of 17 found that compulsive smartphone use is consistently linked to higher scores on eating disorder symptom tests in young people.
- Teens using their phones seven or more hours a day showed a higher likelihood of screening positive for disordered eating compared to those using them around two hours daily, though this finding comes from a small number of studies.
- Calorie-tracking and fitness apps may reinforce disordered behaviors in vulnerable young users, and recommendation algorithms could increase exposure to harmful body-image content without users seeking it out.
- Because most studies were observational snapshots rather than long-term trials, the research shows an association but cannot prove that smartphone use causes eating disorders.
For most teenagers, a smartphone is as essential as a backpack. It’s how they talk to friends, follow trends, and increasingly, track what they eat and how much they exercise. But a sweeping new review of 35 studies covering more than 52,000 people, with an average age of just 17, finds that compulsive phone habits in young people may be closely tied to disordered eating, body dissatisfaction, and emotional overeating.
Published in JMIR Mental Health by researchers at King’s College London, the systematic review found a consistent association between problematic smartphone use and higher scores on eating disorder symptom tests across age groups and more than a dozen countries.
One longitudinal study within the review added a sharper edge to the findings: young people with higher problematic phone use at the outset developed more severe eating disorder symptoms a year later, but the reverse was not true. Eating disorder symptoms at baseline did not predict worsening phone dependency down the road.
Eating disorders affect roughly 8% of women and 2% of men over their lifetimes, with onset typically occurring in adolescence or young adulthood. Many more young people experience disordered eating without a formal diagnosis, with studies estimating that around 22% of adolescents show some form of problematic eating behavior.
Why Teens Are Especially Vulnerable to Smartphone-Linked Eating Disorders
Adolescence is a period when identity is still forming, and social comparison plays a major role in how young people see themselves. Smartphones provide a constant, frictionless channel for that comparison. As Dr. Johanna Keeler, the study’s first author and a Visiting Lecturer at King’s College London’s Institute of Psychiatry, Psychology and Neuroscience, explained: “Adolescence is a key stage of development as individuals evolve their sense of self by observing others. While smartphones might present an easy way for this to happen, being consistently exposed to idealised images can lead them to compare their own appearance with these ‘standards’, leading to poor self-esteem and appearance dissatisfaction, both risk factors for the development of an eating disorder.”
About one in four young people meet the criteria for what researchers call problematic smartphone use, or PSU, a pattern of phone dependency that resembles behavioral addiction. PSU involves an inability to cut back, constant preoccupation with the device, and withdrawal-like symptoms such as anxiety or restlessness when the phone is unavailable. It has already been tied to depression, anxiety, poor sleep, and reduced face-to-face social connection in young people. This review asked whether disordered eating belongs on that list. In the vast majority of included studies, the answer was yes.
It’s worth noting that most studies were observational snapshots rather than long-term trials, which means they can identify a relationship between phone habits and eating disorder symptoms but cannot prove one causes the other. The findings also apply mainly to young people without a formal eating disorder diagnosis.
The Seven-Hour Mark and What It May Mean for Young People
Screen time stood out across several studies. One study examining screen time categories found that young people using their phones for seven or more hours a day showed significantly higher odds of screening positive for disordered eating compared to those using them for around two hours. Users logging three to six hours daily did not show the same elevated risk, suggesting the relationship may become more pronounced at very high levels of use. Higher screen time was also tied to greater body dissatisfaction in multiple studies.
That said, screen time findings came from a relatively small number of studies within the review, and the overall quality of evidence was rated low by the research team due to study design limitations. The seven-hour figure is a signal worth watching, not a hard line.
Calorie Apps, Fitness Trackers, and the Hidden Risk for Teens
Social media’s connection to body image problems in young people is well established. Less examined is the role of calorie-tracking and fitness apps. Researchers note that behaviors central to eating disorders, including compulsive calorie counting, over-exercising, and obsessive body checking, are directly enabled by popular smartphone apps. Built around features designed to maximize engagement, daily streaks, push notifications, gamified progress bars, these tools could make it easier for vulnerable young users to monitor food and exercise in ways that tip from healthy habit into harmful obsession.
The study’s senior author, Professor Ben Carter of King’s College London, put the broader concern plainly: “Smartphones have become ubiquitous in our everyday lives. It is apparent from our study that, even for people without a diagnosis of an eating disorder, the overuse of a smartphone is associated with poor body satisfaction and altered eating behaviours, and is a potential source of distress.”
The authors also suggest that recommendation algorithms may amplify the problem. Platforms learn from user behavior and surface more of what keeps a person engaged. For a teenager already preoccupied with food or body image, that could quietly steer feeds toward thin-ideal imagery, extreme fitness content, and restrictive diet culture, without the user ever deliberately seeking it out. These are proposed mechanisms rather than findings measured directly in the studies, but they align with what broader research on social media and young people has shown.
Emotion Regulation: The Missing Piece
Several studies in the review pointed to difficulty managing emotions as a key connector. Young people who struggle to handle emotional distress are both more likely to reach for their phones compulsively and more vulnerable to disordered eating. PSU may function as a coping strategy that backfires: phones get used to soothe anxiety or sidestep negative feelings, but the habit may gradually erode emotional resilience and deepen exposure to triggering content.
In one study, disrupted sleep was linked to greater emotional distress and worse eating behavior, with heavy phone use acting as a connecting factor between them. For teenagers already navigating the pressures of adolescence, that chain reaction may be especially difficult to interrupt.
Researchers argue that eating disorder prevention programs should start incorporating education about smartphone habits, with targeted guidance on which patterns of use carry the most risk rather than blanket screen time rules. Whether calorie-tracking apps, late-night scrolling, and algorithmically curated feeds turn out to be direct contributors or simply travel alongside deeper vulnerabilities, the authors say those patterns deserve serious attention in efforts to protect young people’s mental health.
Disclaimer: This article is based on a systematic review of observational studies and does not constitute medical advice. The research identifies associations between smartphone use and disordered eating symptoms but cannot establish cause and effect. If you or someone you know is struggling with disordered eating, please consult a qualified healthcare provider.
Paper Notes
Limitations
Nearly all 35 studies used cross-sectional designs, meaning data was collected at a single point in time, which prevents any conclusions about whether problematic smartphone use causes eating disorder symptoms, whether preexisting vulnerabilities drive heavier phone use, or whether the relationship runs in both directions. Most studies relied on self-report questionnaires rather than clinical interviews or formal diagnoses, introducing the possibility of recall error and social desirability bias. Potential confounders including personality traits, psychiatric comorbidities beyond anxiety and depression, and specific app usage patterns were not consistently controlled for. All findings apply to nonclinical populations and cannot be fully generalized to individuals with a formal eating disorder diagnosis. Screen-time threshold findings came from a small subset of studies and should be interpreted with caution. Using the GRADE evidence-grading system, the review team rated most outcomes as “low certainty” and food addiction findings specifically as “very low certainty,” citing the cross-sectional study designs and potential publication bias.
Funding and Disclosures
No financial support or grants were received from any public, commercial, or not-for-profit entities for the research, authorship, or publication of this article. No conflicts of interest were declared.
Publication Details
This systematic review was conducted by Johanna Keeler, Laura Conde Ludtke, Qingyu Yang, Valentina Raschke Rameh, Rebecca Ward, Janet Treasure, and Ben Carter, all affiliated with the Institute of Psychiatry, Psychology and Neuroscience at King’s College London. It was published on March 9, 2026, in JMIR Mental Health, volume 13, article e88572. The study protocol was preregistered via PROSPERO (registration number CRD420250654159). DOI: 10.2196/88572.
