Nine hours of sleep a day cuts obesity risk in boys, new Singapore study shows

Boys who maintain at least nine hours of sleep throughout the week have a 51% lower risk of obesity and significantly less abdominal fat.

A*STAR’s Institute for Human Development and Potential (A*STAR IHDP) has published findings from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort in the journal titled Obesity in October 2025.

This is Singapore’s first study to use magnetic resonance imaging (MRI) to explore how children’s sleep duration relates to different types of fat, particularly abdominal fat which is closely linked to metabolic diseases such as type two diabetes and cardiovascular disease.

The study analysed data from 638 children with an average age of 10.2 years. About half were boys, and participants came from Singapore’s Chinese, Malay, and Indian communities. Sleep duration was measured through caregiver reports and wearable activity trackers. MRI scans were used to map fat under the skin and around internal organs.

Consistent sleep linked to healthier fat distribution

Boys who slept at least nine hours daily throughout the week had healthier outcomes. They showed significantly lower fat across all abdominal regions measured, including visceral fat, which is stored around internal organs.

These boys also had lower levels of a blood inflammation marker that is linked to chronic inflammation and heart disease. Girls showed similar but weaker associations, suggesting possible biological or behavioural differences in how sleep affects fat accumulation.

Weekend catch-up sleep does not compensate for weekday deficits

Many school-age children sleep less on weekdays and try to catch up on weekends. The study found that this pattern did not reduce obesity risk or abdominal fat. Only children who consistently met recommended sleep duration across both weekdays and weekends experienced protective benefits.

“This finding has important implications for parents, schools and policymakers,” shared Dr Shirong Cai, Principal Scientist at A*STAR IHDP and senior author of the study.

She concluded by saying that said that consistent sleep habits throughout the week were important for protecting children’s metabolic health, rather than relying on extra sleep on weekends.

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