Ultraviolet rays reduce levels of hunger-control hormones in the body, which stimulates appetite, but the simultaneous increase in the stress hormone norepinephrine increases fat breakdown, preventing weight gain. It also causes white fat, which stores energy, to be converted into brown fat, which burns energy, according to the study conducted on mice.
The research team at Seoul National University Hospital in South Korea believes there may be a way to harness the benefits of ultraviolet radiation, in a way that does not increase the risk of cancer, in order to treat obesity.
The team discovered that mice that were continuously exposed to ultraviolet radiation for 12 weeks, regardless of whether they ate a normal diet or a high-fat diet, did not gain weight.
The ultraviolet rays caused increased levels of the neurotransmitter norepinephrine, which plays a crucial role in the body's fight-or-flight response. It also helps regulate blood glucose levels.
Increased norepinephrine secretion in the body breaks down fat stores for energy, burning more calories without increasing physical activity, the researchers note.
Although the mice ate more calories when their appetite increased, the body converted them into energy by converting white fat into brown fat before it could be stored under the skin, thus preventing weight gain.
“This study demonstrates the mechanism by which UV exposure can increase appetite while preventing weight gain,” said Dr. Jin Ho Chung, lead researcher and dermatologist at Seoul National University Hospital.
He added: "Exposure to ultraviolet rays not only affects the skin, but also plays a profound role in the body's energy metabolism and homeostasis processes." This does not mean that people should sit in the sun for hours on end without using sunscreen, or sit in a tanning bed.
It is noteworthy that ultraviolet rays damage DNA in cells, which can accumulate over time and cause cancer.
The study was published in the Journal of Investigative Dermatology.
Fascinating!
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