Marc Sorenson, EdD, Sunlight Institute
Those of you who follow this blog remember that one of my posts regarding weight control showed that early-morning sunlight was inversely correlated to body weight and Body Mass Index (BMI). The earlier in the day the sunlight exposure occurred, the slimmer was the figure or physique.
Another scientific paper was recently published that “sheds more light” on the subject of obesity. This research was conducted on mice that were placed on a high-fat diet and then exposed to non-burning ultraviolet radiation (UVR) during a three-month experiment. The mice, without the benefit of UVR, would have been expected to gain weight rapidly, but when they were exposed to UVR, the weight gain was impressively reduced; the UVR treatment achieved 30-40% less weight gain, compared to the expected weight gain with the high-fat diet. The amount of UVR exposure to the mice was proportionally equal to the amount of UVR that a human would be exposed to by standing for ten minutes at noon.
Other benefits included significant reductions in glucose intolerance, insulin resistance and fasting insulin levels (all markers and predictors of diabetes), nonalcoholic fatty liver disease measures and cholesterol. All of these factors, including obesity, are part of a cluster of maladies known as the metabolic syndrome, or MetS, which is indicative of deteriorating health and susceptibility to heart disease, diabetes and death.
Other interesting findings:
Supplementation with vitamin D actually reduced the aforementioned beneficial effects. Dr. Shelley Gorman, one of the authors, made two interesting observations regarding the research:
- “These findings were independent of circulating vitamin D and could not be mimicked by vitamin D supplementation.”
- “It looked like the presence of vitamin D in mice on the high fat diet prevented the [beneficial] effect of UV radiation on weight gain.”
- She also mentioned that the mechanism or weight loss may be dependent on nitric oxide (NO), which originates from diet and can be mobilized by UV radiation to become bioactive.
In another part of the experiment, skin induction of nitric oxide (NO)—also a product of skin exposure to sunlight—reproduced many of the positive effects of UVR, something that vitamin D could not do.
The authors concluded their research thusly: “These studies suggest that UVR (sunlight exposure) may be an effective means of suppressing the development of obesity and MetS, through mechanisms that are independent of vitamin D but dependent on other UVR-induced mediators such as NO.”
Research continues to mount about the positive effects of sunlight that are independent of vitamin D. This should in no way be construed to diminish the vital importance of vitamin D; rather, it is to make a point that sunlight works in many ways, among which are stimulating the production vitamin D, stimulating the production of NO, stimulating the production of serotonin and stimulating the production of endorphins. Why should we be satisfied with any one of these marvelous health aids when sunlight is available? With sunlight exposure, we can have them all.
 Reid KJ, Santostasi G, Baron KG, Wilson J, Kang J, Zee PC. Timing and intensity of light correlate with body weight in adults. PLoS One. 2014 Apr 2;9(4).
 Geldenhuys S, Hart PH, Endersby R, Jacoby P, Feelisch M, Weller RB, Matthews V, Gorman S. Ultraviolet radiation suppresses obesity and symptoms of metabolic syndrome independently of vitamin D in mice fed a high-fat diet. Diabetes. 2014 Nov;63(11):3759-69
 See footnote 4.