A long-term study of the University of California, Berkeley, examined with adolescents whether there is a link between bedtime and the Body Mass Index (BMI).
In a period of 15 years, data from 3.300 teenagers and adolescents concerning sleeping- and eating-behavior, physical activity and screen time were collected and the respective BMI determined. A BMI from 18.5 to 24.9 is regarded to be ideal. Lauren Asanow, director of studies, and her team evaluated the collected data and came to the following finding: “Each hour which they got to bed later caused a rise of the BMI; in a period of five hours as much as 2.1 points.”
It turned out that neither physical activity, time spent on computer, TV or mobile phone nor sleeping duration had a significant influence on this. Only additional unhealthy eating behavior had a further highly negative influence on the BMI.
In spite the fact that the inner clock is shifted backwards in puberty and adolescents temporarily become chronobiologic owls, each hour they are able to go to bed earlier is an absolute benefit for a healthy BMI.
Study: Evidence for a Possible Link between Bedtime and Change in Body Mass Index.
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