Obesity science & practiceDec 22, 2018

Sleep length, timing, and consistency linked to body fat in 8- to 12-year-old children with obesity

Updated Feb 8, 2026

Abstract

Each hour later in weekday bedtime is associated with an additional 6.17 per cent overweight in children with obesity.

Greater day-to-day variability in weekday bedtime is associated with an additional 10.20 per cent overweight.
Increased variability in weekday wake time correlates with an additional 10.02 per cent overweight.
Associations persist after controlling for factors like television screen time, caloric intake, and physical activity.
Later bedtimes and irregular sleep schedules are linked to higher levels of adiposity in children.
Consistent sleep timing may help in managing obesity among high-risk children.

Simplified

OBJECTIVES: Sleep disruption in laboratory studies increases adiposity and decreases glucose tolerance. However, few epidemiological studies have used objective measures of sleep. This study aims to assess associations between sleep duration, timing and regularity with measures of adiposity.

METHODS: This is a cross-sectional study of 188 children with obesity (age: 10.50 ± 1.39 years; body mass index: 29.24 ± 5.04 kg m). Nightly sleep duration, bedtime and wake time were measured by multiple-day actigraphy and parent reports. Per cent overweight (per cent over median body mass index for age and sex) was chosen as the primary measure of obesity status. Objective measures of height, weight, waist circumference, blood pressure, fasting blood lipids, glucose, insulin, glycated haemoglobin and C-reactive protein were obtained. Television screen time and total caloric intake were assessed via parent questionnaire. -2

RESULTS: Each hour later in weekday bedtime was associated with an additional 6.17 per cent overweight (95% confidence interval [CI]: 1.42-10.92). Each hour greater in day-to-day variability in weekday bedtime and weekday wake time was associated with an additional 10.20 (95% CI: 0.50-19.91) and 10.02 (95% CI: 1.55-18.50) per cent overweight, respectively. Associations were similar after controlling for other obesity-related behaviours (television screen time, total caloric intake and physical activity.).

CONCLUSIONS: Among children with obesity, later bedtime and greater variability in bedtime and wake time are associated with greater adiposity, independent of other obesity-related behaviours. Early bedtime and wake time and consistent day-to-day sleep timing may be strategies to reduce adiposity in high-risk children.

Key numbers

6.17%

Increase in Overweight Percentage

Each hour later in weekday bedtime

10.20%

Increase in Overweight Percentage

Each hour greater in day-to-day variability in weekday bedtime

10.02%

Increase in Overweight Percentage

Each hour greater in day-to-day variability in weekday wake time

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Abstract

Key numbers

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