The Sunshine Study: Does it do your weight good?

A couple of weeks ago I heard a news story which referenced the power of sunshine.  Readers who have met me know that my favorite thing in life is sunshine.  I was delighted to hear that science supports something I knew anecdotally (i.e., by my personal experiences); the sun does a mind good.  It follows that what does the mind good will do the body good (tanning excluded!).

The headlines were even better – tantalizing even… early morning sun aids in weight control… or those who spent time in the sun between  8 and 11 a.m. weigh less (smaller BMI) than those who do not get out in the early sun. REALLY?!  I exercise outside almost every morning (walk, bike, run) after 8am but before 12.  Yay!

I do have a low BMI, but I know it is because of my dietary intake and physical activity (it certainly isn’t my genes), I am not inclined to believe that the sun I adore is keeping me thin.  Still, I wanted to learn more about this study so I could give my favorite ‘element’ the kudos and promotion it deserved.

I located the referenced study – referenced in the popular press and linked for you below – and read every single word.  I read and read, paragraph after paragraph, I read and searched and waited… until I got to the very end, past the introduction, the methods, results, discussion, limitations, acknowledgement and the references.  I even used ‘word find’ for goodness sakes FIND: Sunlight or Sunshine.  Nada, nil, zilch.  Sunshine is not mentioned once in the study.

Below I offer a little information from the study, and then the email response from the corresponding author, because of course I emailed her.  I had to be doubly sure I didn’t overlook the part where the people talked about the time they spent in the sunlight.

Participants (54 people) agreed to wear a special light and activity sensor on their wrist (on the outside of their clothing) for 7 days.  This device generated data that the researchers could review, i.e., when the person fell asleep, how long they slept, when they were exposed to light – background, ambient light – and the level of intensity of that light.  The unit of measure for light is LUX.  The participants also completed a 7 day food intake diary and gave their heights and weights (for BMI calculation).  The goal was to see if timing and intensity of light was associated with sleep, eating, or BMI. 

The only finding that was considered ‘real’ was that people exposed to higher levels of light i.e., > 500 lux had lower BMI numbers than people not exposed to light above 500 lux.  This correlation only held if the exposure occurred in the early morning hours. 

It is probable that the light at > 500 lux was from the sun, but there is absolutely no way to confirm this.  Researcher Phyllis Zee kindly responded to my email inquiry and said that with a lux over 200 it is expected that sunlight was ‘involved,’ but the source of light was indeed unknown. Also, I think it is important to note that a BMI even if accurately representing excess adipose tissue is not something associated with the last 7 days!  One BMI point = 6 pounds and well, my BMI is about my last 7 years, not 7 days.

All that being said, Sunshine Makes Me Happy and that is all I need to know.

Reid, K. J., Santostasi, G., Baron, K.G., Wilson, J., Kang, J., & Zee, P. C. (2014). Timing and Intensity ofLight Correlate with Body Weight in Adults. PloS one, 9(4),e92251.

Another "Eight" Myth

As you may know by now, eight 8 ounce glasses of water a day is more an old adage than medical advice. This is largely due to the fact that we do not all weigh the same, and thus don't all need 64 ounces of fluid. Also we don't all do the same things with our bodies, so some need more and some need less.
Today I am writing about a research study on the sleep needs of person's over age 65.
The study was mentioned and explained in a USA Today article by Kim Painter. Her article was good, but it did not explain one issue that I thought was relevant. Being the curious girl I am, I contacted the lead author, Derk-Jan Dijk-Professor of Sleep and Physiology -Director, Surrey Sleep Research Centre in the UK. He forwarded the actual research article to me.
My post today comes from Ms. Painter's article, Dr. Dijk's study and the experts interviewed by Ms. Painter. Of note, no group in the study is getting eight hours of sleep and according to a side bar in the article, the most sleep - in the 20-30 year olds, was just over seven hours and the other two groups, 40-55 and 66 and above were getting six plus hours.
The study explored whether or not the less hours of sleep in the older group was truly a deficit that led to functioning problems during the day or over time. The research indicates that it does not. However, it was a small study and is not conclusive.
The scientists did require that the volunteers be healthy. That was my issue - what defines healthy? Dr. Dijk sent me the article so that I could look at the criteria and he said that I could email him again if I needed more information, but I felt that he had already been generous.
The volunteers did under go a medical and psychological screen at the first visit. They were not to have any sleep disorders and they could not be on any mood or conscious altering drugs (think of any meds for mental illness, many pain meds, and meds for insomnia). The paper did not indicate if weight or chronic disease was a factor. Thus, I am making an educated assumption that the people in the study could have a chronic illness (how many over age 60 do not have one ?) but that the illness had to be controlled.
So the study was cool. The older persons did take longer to fall asleep and historically, older persons do also have sleep disturbance. In the experiment, they did interrupt the sleep of the younger and older subjects, so that everyone had less SWS (slow wave sleep) time. The researchers tested for day time sleep and also for functioning, alertness, energy and relaxation. Most persons who had their sleep disrupted would fall asleep during a designated nap period the next day. What the researchers found was that the older persons did not have that daytime sleep propensity when their sleep was disrupted or shallow - on its own, or when they slept on average, 40+ minutes less than younger persons.
All this meaning, it could just be possible that our sleep needs DO change over time and that we can function well with less sleep. This is far from an agreed upon theory however. Sleep is restorative and effects many different levels of our functioning, from our immune system to our memories. If one lacks hours of sleep or has restive sleep, the replenishment may not occur.
Of note, under normal conditions, it does not appear that six to seven hours of sleep lead to daytime drowsiness, thus - it is NOT normal and should be reported to a physician.
Another thing I liked in Ms. Painters article was a statement by the director of sleep research at the National Institutes of Aging. He introduced the idea of sleep ability vs sleep need. That is interesting. If one's need is greater than one's ability than certainly a sleep disorder may be at hand. However, if need and ability are equal, even at six hours, than one does not need to "fret" over not getting that 8 hours. Certainly, that would be counterproductive and interrupt the sleep more.

I still wonder about the differences that might occur if we compared older persons that are fit and active vs those who are sedentary, overweight and who have diabetes, HTN, or other cardiovascular problems.