“Can you read me another story? I’m thirsty. I’m not sleepy.” For parents of young children, these delaying tactics at bedtime will sound familiar. Though negotiating with a preschooler can be an exercise in futility, a new study suggests that preschoolers who go to bed by 8 p.m. have a much lower risk of obesity when they are teenagers.

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“Just 1 more minute?” The new study recommends a bedtime before 8 p.m. for preschoolers to lower risks of obesity.

The study, published in The Journal of Pediatrics and conducted by researchers from The Ohio State University College of Public Health, provides a scientific basis for bedtimes to which pediatricians and parents can point.

It may come as no surprise that obesity in children is a major public health concern in the United States.

According to the Centers for Disease Control and Prevention (CDC), around 17 percent of children and adolescents aged 2-19 years are obese, which can increase risks for chronic diseases such as type 2 diabetes and heart disease.

The CDC say our society has become dominated by environments that promote eating less healthy foods and being physically inactive.

Examples of negative influences in this regard include advertising of less healthy foods, no safe places in the community to play or be active, limited access to affordable healthy foods, increasing portion sizes, and greater availability of energy-dense foods and sugary beverages.

To further investigate how sleep patterns could affect obesity risk, the researchers used data from 977 children who were part of the Study of Early Child Care and Youth Development. This study followed healthy babies who were born at 10 sites in the U.S. in 1991.

Led by Associate Prof. Sarah Anderson, the team placed preschool bedtimes into three categories: before 8 p.m., between 8-9 p.m., and after 9 p.m.

The children in the study were between 4-5 years of age when their mothers reported their weekday bedtimes.

Later, when the preschoolers were teenagers – about 15 years of age – the researchers linked their bedtimes as preschoolers to risk of obesity.

Results showed that of the preschoolers who went to bed before 8 p.m., only 10 percent were obese as teens, compared with 16 percent of children with the mid-range bedtimes and 23 percent of children who went to bed after 9 p.m.

Interestingly, half of the kids in the study went to bed between 8-9 p.m. Meanwhile, a quarter went to bed before 8 p.m., and the other quarter went to bed after 9 p.m.

“For parents, this reinforces the importance of establishing a bedtime routine,” says Anderson. “It’s something concrete that families can do to lower their child’s risk, and it’s also likely to have positive benefits on behavior and on social, emotional, and cognitive development.”

Routines at home – such as bedtime – can, of course, be influenced by the emotional climate. As such, Anderson and team investigated and recorded the interactions between mothers and their children during playtime.

This so-called maternal sensitivity factors into maternal support, respect for the child’s autonomy, and lack of hostility, say the researchers.

The team found that there was a strong link between bedtime and obesity, regardless of the quality of the maternal-child relationship. However, the children who went to bed the latest and whose moms had low sensitivity scores had the highest risk of obesity.

Additionally, children who were not white, whose moms had less education, and who lived in lower-income households tended to have later bedtimes.

The reason the researchers focused on bedtimes is that they impact the duration of sleep more so than wake times, over which Anderson says parents have less control.

Although putting a child to bed early will not ensure he or she will fall asleep immediately, Anderson notes that having a consistent bedtime routine makes it more likely that the child will ultimately get the amount of sleep they need.

”It’s important to recognize that having an early bedtime may be more challenging for some families than for others. Families have many competing demands and there are tradeoffs that get made. For example, if you work late, that can push bedtimes later in the evening.”

Sarah Anderson, lead author and associate professor of epidemiology

The researchers note that their study does not unravel how sleep time ties into other factors that contribute to weight gain in childhood, including physical activity and nutrition.

Read how being well hydrated could prevent weight gain.