Seasonal Affective Disorder; Sunlight Affects Weight, Appetite, Leptin, Ghrelin

Patients have been asking about SAD/Seasonal Affective Disorder and the effect of daylight on appetite and weight. The days are finally starting to get longer - thank goodness - but many people are still feeling the effects of the long nights and short days. Those who work indoors can suffer even more, heading to work in the morning in the dark, and then heading home at night in the dark; we can feel like cave dwellers! Some can even have Seasonal Affective Disorder (learn more here: http://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/basics/symptoms/con-20021047 )

Can we lose weight by getting morning sunlight?  Well, the jury is still out on this one, but research suggests that there may be a connection between bright morning light and lower weight:

"Timing and Intensity of Light Correlate With Body Weight In Adults"  http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0092251

And here is a good article with an interview with the lead researcher:  http://healthyliving.msn.com/health-wellness/the-morning-light-may-help-you-stay-slim-1  

"We were very interested in looking at the relationship between lighting and how that may be affecting your weight," explained study senior author Dr. Phyllis Zee, director of the sleep disorders center at Northwestern University Feinberg School of Medicine inChicago….Zee said the strongest association was seen in people exposed to light that was at least 500 lux, which is the equivalent of a well-lit indoor room. Outside on a sunny day provides 1,000 lux or higher, while most indoor rooms are about 200 to 250 lux, according to Zee...But, the timing of the light also mattered. Those who were exposed to brighter light earlier in the day were the slimmest."

Previous studies have also shown a connection between light, appetite, metabolism, and weight.  From the PLOS ONE research article:  "Several studies now indicate that morning light exposure influences body fat [3], [4] as well as the level of appetite regulating hormones... leptin and ghrelin [5]...The results of this study demonstrate that the timing of even moderate intensity light exposure is independently associated with BMI….Our findings, similar to those from two different animal models [7], [8] found that changes in the timing of light exposure were associated with body weight independent of caloric intake. One possible mechanism linking light directly to BMI, rather than caloric intake may be the influence of light on the expression and secretion of hormones, such as melatonin."

So, the research is still in early stages, we are not quite sure which hormones are being affected, and how the light might lead to lower weight.  From a practical standpoint, should we do anything?

Well, it can't hurt to get out and get a morning walk in the sunlight.  Heck, it might even help! You may want to consider Light Therapy Lights for Seasonal Affective Disorder, such as: Sunbox, Apollo, Verilux, and Northern Lights. Learn more about light therapy: http://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/in-depth/seasonal-affective-disorder-treatment/art-20048298

• Danilenko KV, Mustafina SV, Pechenkina EA (2013) Bright light for weight loss: results of a controlled crossover trial. Obes Facts 6: 28–38. doi: 10.1159/000348549

Dunai A, Novak M, Chung SA, Kayumov L, Keszei A, et al. (2007) Moderate exercise and bright light treatment in overweight and obese individuals. Obesity (Silver Spring) 15: 1749–1757. doi: 10.1038/oby.2007.208

Figueiro MG, Plitnick B, Rea MS (2012) Light modulates leptin and ghrelin in sleep-restricted adults. Int J Endocrinol 2012: 530726. doi: 10.1155/2012/530726