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Does lack of sleep have a greater impact on obese teens?
Last reviewed: 02.07.2025
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In a recent study published in JAMA Neurology, researchers examined how sleep duration in adolescents impacts the relationship between cognitive function and obesity. The results showed that overweight or obese adolescents experience greater cognitive impairment after reducing sleep compared to normal-weight adolescents.
Obesity is rapidly becoming a major problem among children in the United States. Neurobiological data and cognitive test results link obesity to cognitive difficulties. The multifactorial nature of this association makes it difficult to identify causal mechanisms for cognitive impairment. Neuroanatomical damage can lead to increased food intake and obesity. Biological factors such as insulin resistance and low-grade inflammation can also cause cognitive impairment.
Poor sleep quality is strongly associated with increased fat mass, increased appetite due to high cortisol and ghrelin and low leptin, and poor food choices. Sleep disturbances also affect cognitive function, but it is unclear how exactly reduced sleep affects the relationship between fat mass and cognitive function.
In this study, the researchers hypothesized that sleep deprivation would impair various aspects of cognitive function, and that these negative effects would be more pronounced in adolescents with high levels of body fat compared to adolescents of normal weight.
Unlike previous studies that used only body mass index (BMI) to assess obesity, this study also used body fat percentage (TBF%). Adolescents aged 14 to 19 years were included in the study if they were healthy and did not have sleep disorders, eating disorders, intellectual disabilities or eating difficulties.
The study included three laboratory visits for adolescents and their parents. During the first visit, parents completed dietary and demographic questionnaires. Baseline participant measurements included bioelectrical impedance analysis, cognitive test performance, and weight and height assessment. The subsequent two visits included two randomized orders of two actigraphy-confirmed sleep conditions: sleep restriction of 4 hours and adequate sleep of 9 hours.
The results showed that the negative effects of sleep deprivation on cognitive function were greater in adolescents who were obese or overweight. They performed worse in global cognitive function, cognitive flexibility, fluid cognition, and attention after one night of insufficient sleep.
The use of TBF% highlighted the limitations of using BMI to assess obesity. Higher TBF% was found to be associated with lower cognitive flexibility, fluid cognition, and information processing speed after one night of insufficient sleep. The TBF% cutoff values were significantly higher for all three cognitive domains compared with previously used values for children, indicating that the risk of cognitive impairment is significantly increased only in adolescents with obesity or severe obesity.
With adequate sleep, there was no difference in cognitive function between overweight and normal-weight adolescents. Similarly, in normal-weight adolescents, sleep reduction had no significant effect on cognitive function.
The study found that insufficient sleep had a greater negative impact on cognitive function, including fluid cognition, cognitive flexibility, attention, and processing speed, in obese or overweight adolescents compared to normal weight adolescents.