Gordon Lightfoot writes some folksongs that carry a heavy message (down went the Edmund Fitzgerald!). And light itself is a heavy topic; just ask Stephen Hawking. So did you ever suspect that light could make you physically lighter?

Your body clock responds to the daily light cycle of dawn, daylight, dusk and dark. It influences your metabolism, your hormone secretion, your brain waves and your mood, including your interest in sex.

Now, it seems, if you're regularly exposed to 20-30 minutes of sunlight between 8 am and noon, your BMI will be lower than someone who misses those early rays - even if all other variables are the same.

The effects are due to light's influence on your appetite-control hormones, your glucose control systems or something we don't know about yet. But here's how to decipher the quality of your light exposure:

You need exposure to light that's rated at 500 Lux. A cloudy day serves up more than 1,000, while direct sunlight delivers around 32,000 to 100,000 (so don't overdo it!).

A bright office only serves up around 400 Lux. Moonlight? 1 Lux. A moonless night away from city lights and you're out of Lux.

So take time in the early morning to go outside for 20 minutes; then take a midmorning break and head into the light for another 10 minutes or more. If you're also exercising in the gym or getting your 10,000 steps a day at the mall, you'll get double benefits - and soon feel very en-lightened!

© 2014 Michael Roizen, M.D. and Mehmet Oz, M.D.
Distributed by King Features Syndicate, Inc.