Background and purpose: Sleep is necessary to maintain physical health. Every metabolic disorder especially obesity, can affect the quality and quantity of sleep. The aim of this study was to investigate the relationship between sleep quality and quantity and obesity.

Materials and methods: In this descriptive study, data of 3559 participants aged 20 to 70 years were collected from Yazd Health Study (YaS) using a researcher-made questionnaire. The obesity was determined based on BMI. Data was analyzed using Chi-square test, regression analysis and CI in
SPSS V.18.

Results: The participants were 49.5% male. The prevalence of obesity in males and females was 17.3% and 33.9%, respectively. The lowest rate of obesity was found in people aged 20 to 29 years (12%), and the highest rate was observed in those aged 60 to 69 years old (30.4%). The results showed that people with sleep less than six hours, and more than ten hours were 2 and 2.5 times more likely to become obese, respectively. Individuals waking up in an unwanted time of sleep –three times or more- (47%), having more than three nightmares (33%), taking three or more sleeping pills (51%), and people who had more than 60 minutes delay in falling asleep (17%) were more at risk of  obesity.

Conclusion: Considering the importance of enough sleep, sleep hygiene practices are necessary to improve the quantity and quality of sleep in order to prevent obesity.