Are the lights in your neighbourhood making you fat ?

And God said, “Let there be light”, and there was light. God saw that the light was good, and He separated the light from the darkness. God called the light “day”, and the darkness He called “night”.

Edison invented the electric light. The humans lit their houses, their back yards, their streets, their cities. The lights went on a dusk and off at dawn. The darkness of the “night” was displaced by “the light”.

Living under lights is normal but not natural.

So what happens if you stick a couple of mice into this lighted paradise. Well in a simple word – OBESITY !

Researchers at the University of Ohio played “god” with the lighting in the animal unit. One group of mice got to follow the natural lighting rhythm dictated by the sun i.e. 16 hours of light at 150 lux, 8 hours of dark, pitch dark. The second group got to live in the world of a typical city slicker i.e. 16 hours of daylight and 8 hours of dim light (approx 5 lux of light).

After 8 weeks, the mice living “in the light” weighed 50 % more than those living by the sun’s rhythm. The mice were also pre-diabetic i.e. their ability to handle glucose was shot.

Now for the freaky stuff.

The “in the light” mice weren’t lazy, they exhibited the same activity levels. They weren’t even greedy, they ate exactly the same amount of food.

So what was different ?

The only thing that the researchers could find that was significantly different between the two groups was when they ate. Having the lights on all the time, made eating at odd times an option for the “in the lighters”.

When the experiment was run again, but the mice were only allowed to eat during “normal” times – the huge weight gain didn’t happen.

What is “normal” ?

Of course, “normal” times for mice are somewhat different from humans since they are designed to sleep in the day and run around like crazy all night.

Humans are designed to sleep at night and run around all day. But applying the principle to humans sets off a warning light about eating at “the wrong” time.

The wrong time for us is “late” at night.

So the health gurus that suggest you close the pantry around 8 pm are spot on. If you want to shine under the spot lights, don’t allow the fridge light to come on long after the sun has gone down.

Light at night increases body mass by shifting the time of food intake. Proceedings of the National Academy of Sciences (2010) 107 (43) 18664-18669 ;L. K. Fonken, J. L. Workman, J. C. Walton, Z. M. Weil, J. S. Morris, A. Haim, R. J. Nelson.