Teenage Obesity, Teen Weight Gain Linked to Late Sleeping Patterns
A recent study of sleep patterns for 2,200 Australian school-aged children (9-16 years old) showed that the 'night owls' were twice as likely to be obese, and more than 50 % more likely to be overweight than children or went to bed earlier.
On average the 'night owls' substituted 30 minutes of physical activity with about 48 minutes watching TV, playing video games, and online screen time each day.
Encouraging teenagers to go to bed earlier may help prevent weight gain and improve fitness and physical activity. This article discusses the results and implications of the study
Many parents have been concerned as the growing tendency of adolescents and teenagers to go to bed later and sleep-in. There are been many studies on the sleep deprivation caused by late sleeping patterns. Many teenagers go to bed very late and may have only 5-6 hours of sleep a night on week-days. Some schools have decided to start lessons later in the day to try to counter this. Late sleeping has been generally linked with the increase in the hours spent watching videos, TV and playing online games. While the effects of sleep deprivation on teenagers and children have been well documented, what is the effect of the late sleeping patterns themselves when the hours slept remains the same?
A team of researchers from the University of Adelaide in Australia conducted a study or 2,200 adolescent children to examine whether bedtimes and waking up times affected the health and weight of children aged between 9 and 16 years.
The study involved the use of time interviews and pedometers and data collected on their free time activities.
The results the study were published in the Journal Sleep - Sleep Duration or Bedtime? Exploring the Relationship between Sleep Habits and Weight Status and Activity Patterns
Adolescents were divided into four sleep time pattern groups:
- Late to bed - Late to rise
- Late to bed - Early to rise
- Early to bed - Early to rise
- Early to bed - Late to rise
The use of time by the subjects in the four groups were compared in relation to screen time, time of physical activity, and time spent studying.
Weight status and various social features of the groups were also compared.
The table below summarised the results:
Late Sleeping Patterns
48 minutes per day more
27 minutes per day less
z-score ( 0.66 vs 0.45 )
Likely to be overweight
1.47 times higher
Likely to be obese
2.16 times higher
Likely to exercise
1.77 times lower
Likely high screen times
2.92 times higher
City or Country
Late bedtimes and late wake up times were associated with generally lower physical activities and excess weight problems that were independent of age, sex and sleep duration. The late sleep pattern itself was associated with the differences shown in the study.
As with any of these studies it is hard to go from the association between the various aspects to the cause and effect. Late sleeping may not be the direct cause of excess weight. Over weight adolescents may be less likely to exercise and may spend more time watching screens and may go to bed later. Kids who exercise may be simply tired and go to bed earlier. Nevertheless the study is very informative.
The take home messages from the study are:
- Teenagers who go to sleep earlier appear to be less likely to be obese or over-weight and exercise more than the late sleepers.
- The night owls spent more time watching screens - playing video and computer games, watching TV, using computers or involved with sedentary screen-based activities. When they sleep in, especially on weekends they may miss the opportunities for sports and other physical activities that occur in the mornings.
- Though not included in the study, it is worth noting that food choices and eating patterns may also be affected. Midnight snacks may not be very healthy and may be eaten for the wrong reason. Caffeine laden drinks consumed at night may stop the kids getting to sleep.
- The early sleeper group went to bed about 80 minutes earlier and woke up about 75 minutes earlier than the late sleepers.
- The late sleepers watched videos and TV, played video games or online games for and average of 48 minutes more each day generally between 7 PM and midnight.
- More than 90% of the late sleepers exceeded the 2 hours or less screen time per day recommended by Australian Health Authorities. In comparison, 28% of the early sleepers risers met the recommendation.
- On average late sleepers replaced 30 minutes of moderate to vigorous physical activity with 30 minutes of sedentary activity each day compared with the early sleepers.
- Average Body-mass index (BMI) values were generally higher in late sleepers, who were more likely to be obese and have excess weight issues.
- Late sleepers tended to live in major urban centres, have few siblings, come from lower household incomes and to have part-time jobs.
Benjamin Franklin's famous quote rings true from this study
"Early to bed and early to rise, makes a man healthy, wealthy, and wise,"
Contrast this with the words of my high school maths teacher
"If you go to bed before midnight you are wasting your life sleeping"
How much sleep do most people need:
- Infant (newborn) => 18 hours
- Baby (1 - 12 months old) => 14 -18 hours
- Toddler (1 - 3 years old) => 12 -15 hours
- Young child (5 - 12 years old) => 9 - 11 hours
- Teenager (1 -19 years old => 9 - 10 hours
- Adults - 7 - 8 hours
- Pregnant women - at least 8 hours
© 2011 Dr. John Anderson