Is there a digital clock on your nightstand? Do you fall asleep to the TV? How about the flashing light on a wireless modem? Or like me, is there the light from the City That Never Sleeps streaming through your window? New research shows that even if you can fall asleep with the lights or TV on, if you’re trying to lose weight – you probably shouldn’t. Researchers at Ohio State University looked at how light exposure during sleep affected food intake, glucose tolerance (how well insulin clears glucose, getting it into cells for use) and body mass increases in mice – and what they found might have us all reaching for the eye masks. In the study, the mice were housed in one of three conditions: 24 hours of constant light, a standard light-dark cycle (16 hours of light and eight hours of darkness) or 16 hours of light and eight hours low light. The results showed that, compared with mice in the normal cycle of light-dark, those in the dim light had a significantly greater increase in body mass. The researchers found that mice exposed to a dim light at night for eight weeks had a weight gain of 12g, which was about 50 percent more than mice that lived in a standard light and dark period. This dim light scenario is most like the seemingly negligible light in our bedrooms which may be thwarting our weight loss efforts. Interestingly, even with no difference in activity or food consumption, the mice exposed to dim light ate more at night and gained more weight. This illuminates the notion that a big dinner or late night snacks is not ideal for leaning up. The mice that were in exposed in constant bright light also gained more than the mice under normal light dark cycle, which shows us how metabolism is affected by abnormal sleep schedules like shift work, for example. The link between sleep and body fat is slowly unraveling as we understand more about the body’s internal clock (known as circadian rhythm) and the actions of hormones like leptin and human growth hormone (both of which rise during sleep) and known light sensitive hormones like melatonin. While we learn more, note that light leaking into your sleep environment could be causing: Increased appetite at night Difficulty regulating meal timing during the day Difficulty losing weight in general Excessive cravings or overeating Block out any light leaks and get leaner by: Replacing or covering up digital clocks Turn off electric devices with lights such as computers, stereo systems, cell phones, etc Consider black out shades, particularly if you have street light coming in your bedroom windows Use an eye mask Don’t sleep with the TV on Try candlelight only during the evening, or at least 1 hour before bed turn off electric lights And finally, unless your blood sugar dips too low during the night (causing you to wake frequently) then aim to have your last meal 2-3 hours before bedtime to allow leptin and growth hormone to rise. Healthy hormone patterns and a good night sleep are essential to a healthy, fit body – so lights out!