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Ultraviolet Light Makes You Hungrier… But Prevents Weight Gain


Obesity and metabolic disorders are significant global public health issues, prompting continuous research into innovative prevention and treatment methods. A recent study conducted by dermatologists has revealed that ultraviolet (UV) exposure may play a critical role in appetite and weight regulation. This study found that UV exposure increases norepinephrine levels, decreases leptin levels, and induces the browning of subcutaneous fat, which enhances energy expenditure. These findings, published in the Journal of Investigative Dermatology, offer new perspectives on managing obesity and metabolic disorders.

The Multifaceted Effects of UV Radiation

UV radiation, a common environmental factor, has both harmful and beneficial effects on the skin. While it is known to cause sunburn, photoaging, and skin cancer, UV radiation also contributes to the synthesis of vitamin D, essential for overall health. Researchers at Seoul National University Hospital explored another dimension of UV radiation, focusing on its potential benefits in regulating body weight and metabolism.

The study, led by co-first authors Qing-Ling Quan, MD, PhD, and Eun Ju Kim, PhD, investigated the effects of UV exposure on body weight gain in mice models of obesity. The research team hypothesized that UV exposure to the skin could influence systemic energy homeostasis based on their prior discovery that UV rays regulate the metabolism of subcutaneous fat.

Consistent exposure to UV radiation resulted in increased appetite in both normal and high-fat diet-fed mice due to a decrease in leptin, a hormone crucial for appetite regulation. Despite the heightened appetite, there was no associated weight gain. This effect was attributed to UV radiation enhancing norepinephrine secretion, which decreases leptin levels and promotes the browning of subcutaneous fat, thereby increasing energy expenditure. The excess energy intake driven by increased appetite is converted to heat and burned off, preventing weight gain.

Clinical Implications and Future Directions

Lead investigator Jin Ho Chung, MD, PhD, highlighted the significance of these findings in understanding the effects of UV radiation on energy metabolism and homeostasis. This research opens new avenues for developing obesity and metabolic disorder treatments that leverage the mechanisms by which UV exposure regulates body weight. Specifically, the study’s insight into UV radiation’s role in lowering leptin levels and increasing norepinephrine provides a groundbreaking basis for novel dietary regulation and weight loss strategies.

However, the potentially harmful effects of UV exposure, such as skin aging and cancer, necessitate caution. Co-corresponding author Dong Hun Lee, MD, PhD, emphasized the importance of minimizing UV exposure and protecting the skin with sunscreen. The research team plans to conduct follow-up studies to develop new strategies that mimic the beneficial effects of UV radiation without the associated risks.

The study’s findings suggest that UV exposure influences appetite and weight regulation by altering hormone levels and inducing subcutaneous fat browning. These insights offer promising new directions for the prevention and treatment of obesity and metabolic disorders. Future research will be essential in developing safe and effective therapeutic approaches that utilize the benefits of UV radiation while mitigating its risks.

What do you think of the findings of this new study? Leave your thoughts in the comments below. 

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