UV’s Surprising Deep Effect May ‘Open New Avenues’ to Stop Weight Gain

Could UV radiation stop you from gaining weight? A study suggests maybe it can, but at a cost.

We often hear about the damaging effects of UV radiation on our skin, including sunburn, aging and skin cancer. However, we are increasingly learning that UV exposure can affect our metabolism too.

Previous research has shown that UV exposure can limit diet-induced weight gain in mice, but the exact biochemistry underlying this weight regulation was a mystery. Now, scientists from Seoul National University Hospital have demonstrated that UV exposure increases energy expenditure via changes in fat metabolism.

The full findings can be found in the Journal of Investigative Dermatology.

The team, led by dermatologist Jin Ho Chung, found that mice consistently exposed to UV radiation showed an increase in levels of the neurotransmitter norepinephrine, which plays an important role in regulating our fight or flight response.

One of norepinephrine’s many roles is to mediate metabolic activity in our fat cells, specifically “healthy” brown fat tissue. Unlike white fat cells, which primarily store energy, brown fat increases energy expenditure and produces heat, which keeps us warm. Previously, norepinephrine has been shown to encourage white fat tissue to transform into “beige fat,” which begins to burn energy just as brown fat does.

This process is called “browning,” and it is thought that this is what causes the suppression of weight gain in UV-exposed mice.

But that’s not all. UV exposure also appears to reduce levels of a hormone called leptin, which is a known appetite-suppressing hormone. In other words, UV exposure actually increases the animals’ appetites. But because of their higher energy expenditure, they can easily burn off these extra calories.

“This study elucidates the mechanism by which UV exposure can increase appetite while inhibiting weight gain,” Jin said in a statement. “These findings contribute significantly to understanding the effects of UV radiation on energy metabolism and homeostasis and open new avenues for exploring prevention and treatment strategies for obesity and metabolic disorders.”

He continued: “This research demonstrates that UV exposure not only affects the skin but also plays a deep role in our body’s energy metabolism and homeostasis processes…[and] provides a groundbreaking clue for the development of obesity treatment strategies.”

However, because of the damaging effects of UV exposure to our skin, the researchers have warned against going outside and soaking up the sun’s rays without protection. Instead, they plan to invent new strategies to mimic the activity of UV exposure without its damaging side effects.

“Because UV exposure can accelerate skin aging and promote skin cancer, it is advisable to minimize UV exposure and protect the skin with sunscreen,” co-corresponding author Dong Hun Lee said in a statement. “Thus, our research team plans to conduct follow-up studies to develop new strategies that could mimic the effects of UV radiation for obesity and metabolic regulation.”

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