Around 170 million children and adolescents worldwide were living with obesity in 2024, including 70 million children aged five to nine and approximately 100 million adolescents aged 10 to 19, according to the World Health Organization (WHO). The prevalence of obesity among children and adolescents aged five to 19 has quadrupled since 1990, rising from 2% to 8%.

The scale of the problem extends beyond obesity alone. Around 400 million children and adolescents aged five to 19 were overweight worldwide in 2024, including those living with obesity. The prevalence of overweight, including obesity, in this age group increased from 8% in 1990 to 20% in 2024, according to WHO.

A separate analysis by the United Nations Children’s Fund (UNICEF) highlights a shift in the global burden of malnutrition. Its 2025 Child Nutrition Report found that, for the first time, the global prevalence of obesity among children and adolescents aged five to 19 had surpassed that of underweight, at 9.4% compared with 9.2%. UNICEF also reported that low- and middle-income countries accounted for more than 80% of children and adolescents living with overweight. The findings point to the growing importance of addressing unhealthy food environments alongside individual health needs.

In its first global guidelines on managing obesity in children and adolescents, WHO recommends comprehensive lifestyle interventions as the foundation of care, reserving medicines and surgery for selected cases. The guidelines emphasise that childhood obesity requires sustained medical support and broader action to create healthier environments.

WHO defines obesity as a chronic, relapsing disease characterised by excessive fat deposits that can be managed through effective treatment and care. Childhood obesity is associated with an increased risk of noncommunicable diseases, including type 2 diabetes and cardiovascular disease. Children may also experience stigma, discrimination and bullying, which can adversely affect their mental health and well-being.

Lifestyle changes and mental health at the centre of care

WHO strongly recommends dietary improvements, physical activity and other behavioural interventions as the primary approach to managing obesity in children and adolescents. Treatment should be tailored to individual needs, supported by long-term follow-up and designed to improve overall health and quality of life.

The agency does not recommend weight-loss medicines, bariatric surgery or weight-loss devices for children aged zero to nine. For adolescents aged 10 to 19, approved medicines, including glucagon-like peptide-1 (GLP-1) therapies, may be considered when supervised lifestyle interventions have failed to produce improvements. Bariatric surgery may be considered for adolescents with severe obesity under strict conditions.

“The foundation of obesity care for children and adolescents is not medicine or surgery, but access to comprehensive support that enables healthy eating, physical activity and sustainable behaviour change,” said Dr Luz María De Regil, director of WHO’s Department of Nutrition and Food Safety.

However, clinical treatment alone cannot reverse the growing burden of childhood obesity. WHO has called for policies that make nutritious food and opportunities for physical activity more accessible and affordable. These include regulatory and fiscal measures, alongside action in education, urban planning, transport and social protection.

UNICEF has similarly called for measures to improve school food environments, restrict unhealthy food marketing to children, strengthen food labelling and make nutritious foods more affordable.

The day often ends with one last check of Instagram, a few minutes on YouTube or a scroll through messages before sleep. But what begins as a brief digital break can stretch late into the night, delaying bedtime and keeping the mind engaged when it should be winding down. Researchers are increasingly investigating whether this pattern of digital exposure, through its effects on sleep, may contribute to anxiety and other mental health difficulties among young people.

As World Mental Health Day is observed on October 10, emerging evidence suggests that the relationship between digital media and psychological well-being may depend not simply on how long people spend online, but also on when and how they use it.

A scoping review published in Computers in Human Behavior Reports in March 2026 examined longitudinal research on social media use and sleep among young people. The review found that approximately 70% of the longitudinal studies examined reported at least one negative association between social media use and sleep outcomes. The most consistent links involved later bedtimes and longer periods spent trying to fall asleep, particularly among those with problematic social media habits or who used platforms at bedtime.

The findings are significant because longitudinal studies track participants over time, helping researchers investigate whether digital habits precede subsequent changes in sleep. However, the authors cautioned that many studies relied on self-reported screen use and sleep patterns, limiting the strength of conclusions about cause and effect.

The review also identified an important distinction: total screen time alone did not consistently predict poor sleep. The timing of use and difficulty controlling online behaviour appeared to matter.

When sleep becomes the missing link

Sleep may help explain why certain patterns of digital engagement are associated with poorer mental health. Notifications, emotionally charged content and the pressure to respond immediately can keep users mentally alert. Scrolling in bed can also displace time that would otherwise be spent sleeping.

Insufficient or disrupted sleep can affect emotional regulation, concentration and the ability to manage everyday stress. For someone already experiencing anxiety, a poor night’s sleep may make worries more difficult to manage the following day. Repeated sleep disruption may then reinforce a cycle of distress and further digital engagement.

A systematic review and meta-analysis published in the Journal of Affective Disorders in December 2024 provides a broader picture of this relationship. Researchers assessed 182 studies involving 1,169,396 participants, with 98 studies and 102,683 participants included in the meta-analyses.

Representational image.Image credit:Pexels

The researchers found small but statistically significant associations between general social media use and anxiety and depression. Problematic social media use showed associations with anxiety, depression and sleep problems, alongside lower well-being. Importantly, ordinary social media use was not consistently associated with sleep problems or sleep duration, whereas problematic use was associated with sleep difficulties.

The relationship may also operate in both directions. People who struggle to sleep or experience anxiety may turn to their phones for distraction, reassurance or social connection. This can make it difficult to determine whether digital habits contribute to distress, whether distress encourages more digital engagement, or whether both are influenced by other factors.

Beyond the screen-time debate

The findings raise questions for families, schools, technology companies and public-health professionals. Advising young people to reduce screen time may be insufficient if it does not address bedtime habits, compulsive checking, online pressures and the reasons they turn to digital platforms in the first place.

Digital platforms can also provide friendship, information and mental health support. The challenge is to distinguish beneficial engagement from patterns that disrupt rest and emotional well-being.

As research advances, scientists will need to examine not only how much time young people spend online, but also what they experience there and how digital habits interact with sleep and existing vulnerabilities. The question is no longer simply whether people spend too much time on their phones. It is whether constant connectivity leaves enough room for the rest, recovery and emotional balance that mental health requires.

A study comparing brain scans across three major hormonal transitions finds shared patterns of structural change during puberty and pregnancy, while menopause follows a distinct trajectory.

The female brain undergoes different patterns of structural change during puberty, pregnancy and menopause, according to a study published in Nature Communications, highlighting how hormonal transitions may influence brain development and ageing across a woman’s life.

The research compared longitudinal brain imaging data from 1,095 participants. Researchers applied consistent analytical methods across three groups to investigate whether the hormonal transitions trigger similar or distinct changes in grey matter, the brain tissue involved in information processing.

The findings show that girls transitioning through menarche — the first menstrual period — and women going through pregnancy experienced widespread reductions in cortical grey matter volume. However, the patterns differed across brain regions. Women transitioning through menopause, meanwhile, showed no significant reduction in total or cortical grey matter volume during the study period, although women in the stable premenopausal and postmenopausal comparison groups showed declines.

The results suggest that these major hormonal transitions are associated with distinct patterns of brain remodelling rather than a single process affecting the female brain throughout reproductive life.

Puberty and pregnancy share some changes

The research team examined three cohorts: 142 participants in the puberty group, 110 in the pregnancy group and 843 in the menopause group. The researchers compared participants undergoing each transition with control groups to distinguish transition-related changes from ordinary developmental and age-related trajectories.

In the puberty cohort, 34 girls were assessed before and after menarche. Their brain scans showed significant monthly reductions in total and cortical grey matter volume, a pattern not observed in the stable premenarchal and postmenarchal comparison groups.

Similar changes appeared in women who became mothers. Both first-time and second-time mothers showed significant reductions in total and cortical grey matter volume compared with women who had not given birth. The study estimated monthly reductions of approximately 0.12% in total grey matter volume among first-time mothers and 0.11% among second-time mothers.

MRI Brain scans.Representational image.Image credit:Pexels

Despite these similarities, the researchers found that puberty generally involved greater cortical volume reductions than pregnancy. Their regional analysis covered 74 cortical regions and identified both shared and divergent patterns of change.

In 34 regions, the changes associated with puberty and pregnancy did not differ significantly from each other, while both showed greater reductions than the menopausal transition. These areas were concentrated in the prefrontal, parietal and temporal association cortices, which are involved in higher-order functions.

Other regions, particularly those associated with sensorimotor processing, showed a stepwise pattern in which the decline was greatest during puberty, followed by pregnancy and then menopause.

The authors caution that structural changes should not automatically be interpreted as evidence of damage. The study examined brain volume rather than directly measuring cognitive ability or the functional consequences of these changes.

Menopause presents a different pattern

The findings for menopause differed from those for puberty and pregnancy. Women who transitioned from premenopause to postmenopause during the study showed no statistically significant reduction in total or cortical grey matter volume. In contrast, the stable premenopausal and postmenopausal groups showed significant declines over their respective observation periods.

The researchers suggest that this pattern may indicate an attenuation of age-related volume decline during the menopausal transition itself. However, they stress that this interpretation remains preliminary, and the absence of a significant reduction does not establish that the brain undergoes no changes during menopause.

The study also has limitations. The three cohorts were drawn from different datasets and scanned using different MRI systems. Hormone measurements were not available in a harmonised format across all groups, preventing the researchers from directly comparing hormone levels with brain changes throughout the lifespan. Menarche and menopause were also classified using self-reported information rather than detailed clinical staging.

The findings add to a field in which women’s brain health, particularly during reproductive transitions, remains comparatively understudied. The authors call for future research combining repeated brain scans with hormonal, reproductive, psychological and social data.

By examining puberty, pregnancy and menopause within a common analytical framework, the study provides a more detailed picture of how structural brain changes vary across these transitions. It also underscores the need to investigate each stage separately rather than treating the female brain as following one continuous pattern of hormonal change.