Matthew J. Edlund M.D.

The Power of Rest

Endless Jet Lag

Body clocks change what you eat

Posted Mar 26, 2017

Aphiwat Chuangchoem/
Source: Aphiwat Chuangchoem/

Body Clocks and Food

The world is filled with very different kinds of folks  - and I'm not referring to politics.  There are night people and day people, owls and larks.  Researchers have been trying for decades to determine what else is different about them, from their DNA to their diets.  Now there’s new data demonstrating owls eat very differently from larks.

Owls like sugar. A lot.  One reason is that owls who work in our lark work world experience perpetual jet lag, with major effects on sleep, performance, and behavior.   And therein lies lessons for the majority of us,  who are neither extreme lark nor extreme owl.

What Was Found

The Finrisk and Findiet studies took a random sample of Finns across the entire country aged 25-74. Finland has a lot of cardiovascular disease.  Researchers and the government want to know why.  So they used a short version of the Horne Ostberg scale for morningness and eveningness  and discovered: 

1.Owls eat less than larks in the morning, but more sugar.

2. As the day goes on, they eat yet more sugar than larks.

3. Come weekends, they eat twice as often as larks – and more sugar and fats.

Look at the data further and reasons why this might happen begin to appear:

A. Four times as many owls (32.1%) report insufficient sleep compared to larks (8.7%).

B. Significantly more reported insomnia

C. Far fewer owls rated themselves as having good physical fitness (34.8%) versus larks (55.2%) though owls in the study were on average 9.5 years younger than larks.

Clocks, Sleep, and Food

We are built on time.  Time rules life.  Break our inner time, and physiology may change with unpleasant consequences. 

People who sleep too little crave more sugar and fat.  In short term experiments, partial sleep deprivation makes most of us look pre-diabetic.

Things get worse when clocks fall out of synch.  That’s what happens to owls who try to work 9-5, a more common experience in a country like Finland than the US, where work hours now creep through the whole 24 hour spectrum.

In most human experiments, eating during the night ends up with more calories taken in, eating more sugar and fat, with irregular hours of eating.  That’s what breakfast in the morning means to many owls – eating at night.

And their tendency to want to eat later ends up with more sugar and fat consumed later in the day. 

Which is worse, blowing out biological clocks or getting insufficient sleep?  It’s hard to study this in working people, where the two often go together.

In animals like mice, controlling the time of eating means far skinnier mice than when allowing them to eat around the same clock - even when it's the exact same amount of food.  And sleep deprivation, even minor, leads to eating more, particularly more sugar and fat.

Interestingly, other reports from the Finrisk study do not show owls as weighing much more than larks.  Their overall intake of calories was the same.  Yet other studies show more abdominal fat when body clocks are misaligned.

Which brings us to America.

The American Challenge

When people have jobs today, they often find they never end, even in retirement.  Work extends into “leisure” hours in many businesses.  For many professionals, unless work is specifically and carefully given off to others, the 24/7 cycle is pretty much endless.

Technological changes continue to increase the tendency for work all around the clock.  Yet they have also increased the desire and opportunity  for 24/7 play.  Kids can run video games throughout the night.  People can and do text message while they drive, walk, work, even at times when they’re supposed to sleep.

The result is a new kind of endless jet lag for many throughout the world.  Unlike owls who must work at hours that don’t fit their internal clocks, much of present day jet lag is selected by job sites and types, but also by people’s shifting ways of socializing.

Does this explain why investors are willing to spend billions on doughnut companies? Or why you find candy at the edge of your pillow when you check into a hotel?

Humans crave sugar, but jet lag and insufficient sleep make us crave it all the more.  If the World Health Organization is correct and exogenous sugar is a carcinogen, the consequences are not good.

But there are many other consequences from internal jet lag  – like poorly rated health and fitness, weight gain, insufficient sleep, a greater tendency to smoking. Those are just some of the results for owls trying to living in the lark work world.  The Finrisk study tells us a lot about owls, but more about what we are doing to ourselves.

Body clocks change almost everything about us – what we eat, when we sleep, how we perform.  By timing life, they time the intelligent aspects of our lives.  One of our more  intelligent choices can be to heed their prescriptions, and live by our inner time whenever we can.

No matter what our employers or friends think.