Table 1 Summary of major studies reporting an association between short sleep duration and obesity.

First author, publication year, country	Number studied, age group	Design	Key findings
Locard,¹⁷ 1992, France	1031, 5‐year‐olds	Cross‐sectional, case–control	Short sleep duration was associated with obesity (OR 4.9); this was independent of watching TV

Kagamimori,¹⁴ 1999, Japan	9668, 3‐year‐olds	Cross‐sectional, case–control Toyoma cohort study	Frequency of sleeping <10 h was greater in obese children (29.3%) v that in non‐obese children (13.7%)

Vioque,²⁷ 2000, Spain	1772, ⩾15‐year‐olds	Cross‐sectional	Prevalence OR for obesity 0.43 (CI 0.27 to 0.67) for sleeping ⩾9 h v ⩽6 h; prevalence OR for obesity was 24% lower for each additional sleeping hour/day

von Kries,²⁸ 2002, Germany	6862, 5–6‐year‐olds	Cross‐sectional	Short sleep duration was associated with overweight, obesity and increased body fat percentage; adjusted OR for obesity 0.52 (CI 0.34 to 0.78) for sleeping 10.5–11 h and 0.46 (CI 0.28 to 0.75) for sleeping 11.5 h

Sekine,²¹ 2002, Japan	8274, 6–7‐year‐olds	Cross‐sectional, based on Toyoma cohort study	MOR (adjusted for age, parental obesity, physical activity, watching TV, frequency of eating breakfast, snack frequency) v ⩾10 h was 1.49 (CI 1.08 to 2.14) for 9–10 h, 1.89 (CI 1.34 to 2.73) for 8–9 h and 2.87 (CI 1.61 to 5.05) for <8 h; ORs for boys were greater than for girls

Gupta,¹¹ 2002, USA	383, 11–16‐year‐olds	Cross‐sectional Heartfelt study	Only study to use 1‐day actigraphy; short sleep associated with obesity and greater body fat; adjusted OR for obesity decreased by 20% for every hour of increased sleep

Agras,² 2004, USA	150, 9½‐year‐olds	Prospective study of newborn infants from birth to 9.5‐year‐olds	Negative correlation between hours of sleep and overweight (−0.21); overweight children sleep less than 30 min on average than children with normal weight, the difference was mainly in daytime sleep; hours of sleep were negatively correlated with high activity levels

Gibson,⁹ 2004, UK	1294, 7–18‐year‐olds	Cross‐sectional, national diet and nutrition survey of young people	Obese children spent less time in bed (10–20 min 1st quintile of age‐adjusted BMI v 5th quintile), but this was statistically significant only in boys

Reilly,²⁰ 2005, UK	8234, 7‐year‐olds	Children of the 90s (ALSPAC) Bristol	25 factors examined at age 30 months that could predispose to obesity at age 7 years; 8 factors found to be significant, including short sleep duration; OR v 12.5 h of sleep was 1.04 (CI 0.76 to 1.42) for 11–11.9 h; 1.35 (CI 1.02 to 1.79) for 10.5–10.9 h; 1.45 (CI 1.10 to 1.89) for <10.5 h

Padez,¹⁸ 2005, Portugal	4511, 7–9‐year‐olds	Cross‐sectional	OR v 8 h sleep; overweight: OR 0.46 (CI 0.40 to 0.51) for 9–10 h, 0.44 (CI 0.38‐0.49) for ⩾11 h; obesity: OR 0.44 (CI 0.40 to 0.47) for 9–10 h, 0.39 (CI 0.35‐0.42) for ⩾11 h

Knutson,¹⁵ 2005, USA	4486, 15–18‐year‐olds	Cross‐sectional, national longitudinal study of adolescent health	Results significant for men only; linear regression: sleep duration significantly predicted BMI z score (β = −0.08, CI −0.12 to 0.03); logistic regression: sleep duration predicted risk of overweight (OR 0.90, CI 0.82 to 1.00)

Chaput,³ 2006, Canada	422, 5–10‐year‐olds	Cross‐sectional, “Quebec en Forme” project	MOR of obesity v 12–13 h sleep was 1.42 (CI 1.09 to 1.98) for 10.5–11.5 h sleep, 3.45 (CI 2.61 to 4.67) for 8‐10 h sleep; waist circumference negatively correlated with sleep duration (r = −0.24), but only significantly in boys

Chen,⁴ 2006, Taiwan	656, 13–18‐year‐olds	Cross‐sectional, case–control	High adequate sleep (defined as 6–8h sleep/night on >4 weekdays/week) was associated with non‐obesity, OR 1.74 (CI 1.3 to 2.4)

ALSPAC, Avon Longitudinal Study of Parents And Children; BMI, body mass index (kg/m²); MOR, multivariate odds ratio, TV, television.