Teenagers who go to bed early are much less likely to be obese and have a better chance of being physically fit, compared to peers go to sleep late, researchers from the University of South Australia reported in the journal Sleep. The authors added that teenagers who go to bed later but sleep the same number of hours each day as those who put their heads down earlier have a higher risk of becoming overweight and unfit.

Dr Carol Maher, Professor Tim Olds and Lisa Matricciani set out to determine whether bedtimes and waking up times might have an impact on the health and weight of 2,000 Australian children aged between 9 and 16 years. They also gathered data on their free time activities.

Dr Maher said:

“We found that kids who went to bed late and got up late were 1.5 times more likely to become obese and 2.9 times more likely to be physically inactive.

The night owls more often spent their free time playing computer or video games, watching TV or engaged in other sedentary or screen-based activities.

While scientists have already made the connection between less sleep and poor health outcomes around obesity and fitness, what is interesting and new here is that the timing of sleep may be an important factor in predicting health in young people.” “

Maher explained that teenagers tend to stay up till late and get up late. This study should remind people of the dangers of allowing those habits to become extreme ones.

Dr. Maher said:

“We know that evenings tend to be the time of day when there are more sedentary activity options.

The most attractive TV programming is in the evening and it is a time when people hop onto facebook or socially interactive online gaming options so the incentives are there for teenagers to stay up and stay sedentary. At the same time, when they sleep in they are missing the opportunities for sports and other physical activities that tend to be held or undertaken in the mornings.” “

The researchers found that those who regularly went to bed earlier and got up early did approximately 27 minutes more of vigorous exercise than their counterparts who turned in and got up later.

Teenagers who go to bed late generally spend about 48 minutes longer watching TV, going online or playing video games than they early-bird peers. The authors worked out that the night owls replaced 30 minutes of moderate to vigorous physical activity with sedentary pursuits each day.

The following circumstances are linked to a higher percentage of teenage night owls:

  • Those who live in large cities
  • Children from lower socioeconomic households
  • Children with part-time jobs
  • Children with the fewest siblings

Dr. Maher said:

“It is only when you do the research and unpack the dynamic relationships between health and habits that you find trends that can potentially be altered with modifications to behaviour and the social environment.

The research may help to support education around teen-age health and give them the knowledge to improve their own health and well being. “

Benjamin Franklin’s quote: “Early to bed and early to rise, makes a man healthy, wealthy, and wise,” perhaps should have had the following added “so start when you are young and get a head start.”

The amount of sleep people need depends on various factors, such as the quality of their sleep, health, age, how much exercise they have done, when they last ate, etc. A newborn baby needs up to 18 hours sleep each day, while an adult usually needs between seven and eight.

Below is a rough estimate of how much sleep humans need each day, according to age:
(Source: National Health Service, UK)

  • Infant (newborn) – 18 hours
  • Baby 1 to 12 months old – 14 to 18 hours
  • Baby/toddler, 1 to 3 years old – 12 to 15 hours
  • Young child, 5 to 12 years old – 9 to 11 hours
  • Teenager – 9 to 10 hours
  • Adults – 7 to 8 hours
  • Pregnant women – at least 8 hours

Effects of sleep deprivation

Written by Christian Nordqvist