Could Sun Exposure Keep Obesity and Diabetes at Bay?

A little bit of sunshine may slow the onset of obesity and symptoms of type 2 diabetes, according to a new study in the journal Diabetes.

Researchers in Australia studied how ultraviolet light exposure impacts the development of obesity and diabetes in mice. After feeding the mice a high-fat diet to induce obesity and diabetes, they exposed the mice to moderate levels of ultraviolet radiation.

The light exposure appeared to suppress weight gain and signs of type 2 diabetes, such as insulin resistance and abnormal glucose levels. Next, the researchers investigated how it produced these effects.
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“The potential ability of sunlight to suppress weight gain is not through vitamin D, but occurs at least partially through nitric oxide,” says study author Shelley Gorman, PhD, a research fellow at the Telethon Kids Institute in Perth, Australia.

She and her colleagues applied a cream containing nitric oxide—a compound the skin releases after sun exposure—to some of the mice, while giving the others vitamin D supplements. The cream appeared to produce the same benefits as ultraviolet exposure, while the vitamin D didn’t seem to have an effect. 

Given that mice are nocturnal, covered in fur, and not often exposed to much sunlight, the researchers stress that the results should be interpreted cautiously.

Because these are preclinical investigations, Gorman suggests that primary care providers encourage their patients to seek advice about sun exposure and safety from bodies like the American Cancer Society.

“However, by doing regular exercise outdoors, we all may be able to achieve a ‘double-whammy’ of the positive benefits of moderate sun exposure and exercise for weight and diabetes control,” she says.

The lower doses of ultraviolet radiation the researchers used to emulate moderate sun exposure approximated the levels measured in about 2 to 3 minutes of midday summer sunlight in Perth, Australia, where they conducted their study.

“The science tells us that the quantity of sunlight needed to suppress weight gain and signs of type 2 diabetes was only a low dose, insufficient to burn skin,” Gorman says. “We continue to advise a sensible approach to sun exposure.”

Gorman emphasizes that more studies are needed in humans to be able to translate their findings. She and her colleagues have many directions they would like to explore in their continued research.

“As a starting point, we would like to determine if we can intervene, that is, use sun exposure or ultraviolet radiation to induce weight loss and the signs of type 2 diabetes in already obese people,” she says.

—Colleen Mullarkey

Reference

Geldenhuys S, Hart PH, Endersby R, Jacoby P, Feelisch M, Weller RB, et al. 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.