Growing Up Thinner

Go to bed early.  Wake up ten years later slimmer than your peers.  Is weight control really this simple?

Perhaps.

The tantalizing question remains – does more closely fitting your biological clocks and getting more sleep equal less obesity? Recently, researchers looked over data from a study that gathered evidence from 1991 on a thousand kids.  The paper from the Journal of Pediatrics, reported by epidemiologists from Ohio State, showed a biologically enticing dose response curve:

Four and half year olds who went to bed were obese 10% of the time ten years later; those who went to sleep between 8 and 9 had an obesity rate of 16%; those who went to bed past 9 had a rate of 23%.

The authors went looking for the expected confounders.  Wealthier, more educated families have fewer obese kids.  Obese mothers more frequently have obese children. These and other factors were statistically controlled as well as the data allowed.

The obesity rates remained very different.

So why would earlier bedtimes lead to better weight control in kids a whole decade later?  Here are some possible explanations:

Biological Clocks

Time rules life.  Humans are not machines.  A woman who eats the same foods, runs the same number of miles, and does the same job will have a markedly different weight depending on whether she goes to bed at 10 PM or 6 AM.  Shift workers know this in their bones – and their waistlines.

The same is also true of children.  Except children’s clocks are changing rapidly. When you’re born, you may sleep fourteen to sixteen hours, of which almost two-thirds may be REM sleep, critical to brain development.  Your “bed time” as a toddler may be 6 or 7  PM.  By the time you’re a senior in high school, your preferred biological sleep time may be 1 AM and your daily sleep need for maximum performance and contentment 10 hours – of which the average high school senior may see 7 hours or less.

Sleep, and sleep need, changes throughout the life cycle, but far more in childhood than later on.  Could it be that putting kids to be earlier, at times more fitting their biological clocks, made for better weight control?  There’s much evidence arguing it’s a factor.

Sleep Amount

Whenever populations go to bed earlier, the assumption is that this means more sleep time.  For adults, that is clearly not the case.  Work schedules, child rearing and school times have major effects on when people go to sleep – often in opposition to when their body clocks tell them they need it.

However, putting kids to bed earlier may well result in more sleep time.  Recent research would argue that kids today, of all ages, get less sleep time than they need for optimal school, mood, and health performance.  So in this study, putting kids to bed earlier probably meant they got more sleep time – and those kids weighed less ten years on.

Regularity of Pattern

Often it’s not easy putting kids to sleep.  Even in the distant past of the 1990s, when this study was started,  kids had lots to do at night besides going to sleep. So getting a kid into bed at 8 PM probably demanded more parent time and scheduling muscle than letting them go to bed later.

Just as time rules life, pattern changes life.  People who do the same healthy things consistently, day by day, live longer and get less sick.

It is quite possible having early times of sleep also signaled greater regularity of behavioral pattern for the kids in this study,  particularly when compared with those who went to bed later than 9.

Bottom Line

There’s lot of evidence that people who sleep less gain more weight.  There’s plenty of evidence shifting one’s biological clocks away from their norm provokes weight gain.  But there’s been little evidence that just going to bed earlier, particularly in kids, means lower weight when they’re  teenagers.

What this and other studies argue is that lifestyle matters – a lot.  It may matter more in childhood, when the brain and body are changing, shifting, and adapting more rapidly than when we’re adults.

But the same pattern of ceaseless change is true of adults as well.  Most of our bodies are rebuilt in a matter of weeks.  Who you are tonight is different from you are tomorrow.  A constantly renewed, retooled, and remade human is how we survive and thrive.

So it makes sense that the patterns of what we do – when we eat, when we sleep – changes that entire rebuilding cycle.  And how we more effectively eat, move, and rest, results in longer lived, happier people.

Even, it turns out, less obese ones.