For VOA Learning English, this is the Health & Lifestyle report.

Getting a good night's sleep tonight could guard children against weight gain in the future.

According to a new study, putting preschoolers in bed by 8 p.m. could reduce their chances of becoming overweight or obese later in life by half. Preschoolers are children around the age of 4 or 5.

The term ‘obese' refers to calculations of your Body Mass Index, what doctors call BMI. They use a person's height, weight and age to assess their amount of body fat. BMIs help tell whether a person is underweight, normal, overweight or obese.

The World Health Organization says obesity can lead to serious long-term health problems like diabetes, heart disease and stroke.

Researchers from the Ohio State University's College of Public Health have found that young children who go to bed after 9 p.m. are twice as likely to be obese later in life. The researchers wrote their findings in The Journal of Pediatrics.

The lead author of the study is Sarah Anderson. She is an associate professor of epidemiology. She studies how diseases spread and how they can be controlled. Anderson says that, for parents, the results of the study support the importance of creating a bedtime routine.

She says that having a usual bedtime routine is something "families can do to lower their child's risk" of becoming overweight.

A usual, early bedtime, Anderson adds, "is also likely to have positive benefits on behavior and on social, emotional and cognitive development."

Researchers used data from 977 children for the study. These children are part of a larger project called the Study of Early Child Care and Youth Development. The project follows healthy babies born in 1991 in 10 U.S. cities.

The children were 4 ½ years old when their mothers reported their usual weekday bedtime. Researchers then divided the children into three groups:

• those who went to bed by 8 p.m. or earlier,
• those who went to bed between 8 p.m. and 9 p.m. and
• those whose bedtimes were after 9 p.m.

When these children turned 15 years old, the researchers looked at their rates of obesity. Of those with the earliest bedtimes, only one out of 10 was obese. Of those who went to bed between 8 and 9 p.m., 16 percent became obese. And out of those with the latest bedtimes, 23 percent became obese.

Anderson said putting children in bed early does not mean they will immediately fall asleep. But, she adds, it makes it "more likely that children will get the amount of sleep they need to be at their best."

But Anderson says it is important to understand that having early bedtimes may be harder for some families than others. She says that, "families have many competing demands and there are trade-offs that get made." For example, she says, if some parents work late, that can push the children's bedtimes to later in the evening.

Is childhood obesity a worldwide problem?

Obesity among children in the United States is a major health concern. About 17 percent of children and teenagers in the U.S. are considered obese. That is according to the Centers for Disease Control and Prevention.

The World Health Organization reported in 2014 that the number of overweight babies and young children worldwide had increased from 31 million in 1990 to 44 million in 2012. If that trend continues, the WHO warns, there will be 70 million obese children in the world by 2025.

I'm Anna Matteo.

Reporters in the VOA Newsroom put this report together. Anna Matteo adapted this story, adding additional information from World Health Organization reports. Ashley Thompson was the editor.

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preschool - n. a school for very young children

obese - adj. fat in a way that is unhealthy

assess - v. to make a judgment about (something)

epidemiology - n. the study of how disease spreads and can be controlled

routine - n. a regular way of doing things in a particular order

cognitive - adj. of, relating to, or involving conscious mental activities

data - n. facts or information used usually to calculate, analyze, or plan something

trade-off - n. a situation in which you must choose between or balance two things that are opposite or cannot be had at the same time

trend - n. a general direction of change