Staying up late on weekends may drive excess weight gain in school-aged children, possibly due to 鈥渟ocial jet lag鈥� disrupting their ability to process food efficiently.
suggests that children who get less than are more likely to become overweight, but less is known about the effect of inconsistent bedtimes.
To learn more, at the University of Helsinki, Finland, and her colleagues took body measurements from more than 10,000 children aged 9 to 11, who were asked about their sleep routines. Half of the children were measured again 2.5 years later.
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The initial measurements showed that the children who reported going to bed later on weekends compared with school nights had a higher waist-to-height ratio than those with consistent bedtimes throughout the week. They also had a higher body mass index (BMI), which is calculated from height and weight, and was adjusted for the children鈥檚 age and sex.
Going to bed two hours later on weekends, for example, was associated with a 2.4-centimetre larger waist circumference and a 0.32 higher BMI in children measuring 148 centimetres tall, after adjusting the results to account for sleep duration and certain lifestyle factors, such as screen time.
Late weekend bedtimes were also associated with increased rates of weight gain during the 2.5-year follow-up period.
For example, 11-year-olds who went to bed two hours later on weekends than they did on school nights had a 0.6-centimetre greater increase in waist circumference during the follow-up, compared with the participants with consistent bedtimes.
The researchers acknowledge in their research paper that the children self-reported their bedtimes, which could affect the accuracy of the results. People often say they go to bed earlier than they actually do, they wrote.
Nevertheless, at Northwestern University, Illinois, says that staying up on weekends 鈥� a phenomenon known as social jet lag 鈥� has also been linked with .
This may be because it disrupts our circadian rhythms, or body clocks, which affects our ability to process food efficiently, he says.
Going to bed late on weekends often means snacking later, then sleeping in and having delayed meals during the following days, says Cedernaes. Our bodies don鈥檛 process food as well outside of our normal eating schedules, he says.
Cedernaes recommends encouraging children to go to bed at the same time every night throughout the week. Limiting screen time and encouraging physical activity can help to achieve this, he says.
Journal of Sleep Research
