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Beyond the Burn: Sun Triggers Hunger, Too

August 12, 2022

It’s more than fresh air making stomachs grumble in the summer; new research shows it might actually be the sunshine.

A study published in the journal Nature found that exposure to ultraviolet rays from the sun can trigger metabolic changes in the body that drive hunger, especially in men.

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“People, specifically men, with solar exposure are more likely to seek food, increasing their caloric intake,” said Devika Umashanker, MD, medical director of medical weight loss with Hartford HealthCare. “This behavior can be negative as it can increase metabolic disease risk factors such as obesity, cardiovascular disease and diabetes.

Sun exposure on the skin, the researchers found, triggers an increase in the production of ghrelin, the hormone signaling hunger. It is suppression of ghrelin that is part of the focus of weight loss surgery, Dr. Umashanker said. Surgically reducing the size of the stomach, where much of the body’s ghrelin supply is produced, limits the amount production and, therefore, hunger triggers.

“We know that a large percentage of ghrelin is located in the stomach, which is why surgical weight loss can be effective,” she said. “It’s interesting to now know that this hormone is also located on the skin and can be triggered by solar exposure, specifically in men.”

The study demonstrated that a tumor protein, p 53, also located on the skin, is damaged by solar exposure in men, resulting in an elevation of ghrelin and an increase in appetite. However, this is not seen in women because their high level of estrogen serves as a protective mechanism against p 53 damage.

With the new research highlighting the connection between sunshine and hunger, she said awareness is key to controlling unnecessary weight gain.

“My recommendation would be to be aware that your hunger levels may increase when in the sun for prolonged periods, and be prepared with healthy snacks to help curb the appetite,” Dr. Umashanker said.