With the rising popularity of the “sunbathing back” trend tied to traditional “Sanfu health care” practices, many people believe that sunning their backs can help “remove dampness” or even aid in weight loss. Social media is filled with claims like “sunbathing backs burns fat,” making this seemingly simple wellness practice a natural remedy for some. However, this trend carries hidden dangers.
A woman from Zhejiang, known as Ms. Wang, eager to lose weight quickly, began her own “sunbathing back” routine. She deliberately exposed herself during peak UV hours—from noon to 2 pm—wearing only a thin camisole in an open area near her home, convinced that “the hotter, the better.”
For the first nine days, she sunbathed two hours daily and was encouraged by a 4-pound weight loss, proudly sharing her “revitalized” feeling on social media. But on the tenth day, she woke up feeling violently nauseous, followed by severe muscle pain, dizziness, and difficulty standing. Her family noticed her skin was bright red, lips dry and cracked, and her urine output had dropped by half. She was rushed to the hospital.
Emergency tests revealed alarming results: her blood creatinine was three times the normal level, and her creatine kinase skyrocketed to 100,000 units—far beyond the normal upper limit of 200. She was diagnosed with hyperosmolar dehydration, acute pre-renal kidney injury, and rhabdomyolysis syndrome.
Doctors explained that Ms. Wang’s prolonged exposure to high heat caused excessive sweating without proper hydration, leading to severe dehydration and concentrated blood, which drastically reduced kidney blood flow. The heat also caused widespread muscle cell damage and rupture, releasing large amounts of myoglobin that clogged the kidney tubules like a landslide blocking a river. This double assault severely impaired her kidney function and put her at risk of fatal acute kidney failure.
For safe sunbathing, doctors recommend limiting exposure to times with lower UV indexes (usually below 5) and milder temperatures, such as early morning (7–9 am) or late afternoon (5–7 pm). Start with just 10 minutes and gradually increase to 20–30 minutes, with a total daily limit of no more than one hour.
Preparation should include wearing loose, breathable long sleeves to avoid direct skin exposure, and drinking electrolyte-rich fluids like saline water or sports drinks beforehand. High-risk groups—including the elderly, children, pregnant women, people with high blood pressure, skin diseases, or those on photosensitive medications—should avoid this practice altogether.
Experts warn that any weight lost from excessive sun exposure is mostly dehydration, which will quickly return once rehydrated—and the kidney damage risk is not worth it. They stress that weight loss should not come from dehydration and wellness trends should never be blindly followed.
If symptoms like dizziness, palpitations, nausea, or significant decrease in urine output occur during sunbathing, stop immediately, move to a cool place, apply a damp towel to areas with large blood vessels (neck, armpits), and drink warm water. If symptoms persist or worsen, seek medical attention promptly.
