As the world struggles to cope with the effects of extreme weather events, particularly heatwaves, a new study suggests that sunlight not only makes us hot and sweaty, but it also makes us hungrier. Researchers discovered that sunlight stimulates a unique appetite-stimulating hormone in men.
A team of researchers from Tel Aviv University’s Sackler Faculty of Medicine’s Department of Human Genetics and Biochemistry investigated environmental cues such as solar ultraviolet (UV) exposure that cause unique changes. They discovered that exposure to solar rays has more complex effects on male physiology than previously thought.
According to the study published in the journal Nature Metabolism, ‘solar exposure induces food-seeking behaviour, food intake, and food-seeking behaviour and food intake in men, but not in women’. The researchers maintained that gender differences have a significant impact on health and behavior. However, whether men and women react differently to environmental cues such as ultraviolet (UV) radiation is unknown.
The study on mice found that exposure to ultraviolet light increased food-seeking behaviour, food intake, and weight gain, with a sexual dimorphism toward males. ‘ In both mice and human males, increased appetite is associated with elevated levels of circulating ghrelin’, according to the study.
Over a three-year period, researchers examined data from 3,000 participants in a national nutrition survey and discovered that only men increased their food intake during the summer, consuming an extra 300 calories per day. While the amount consumed is small, if consumed continuously over a long period of time, it can result in weight gain.
The desire to consume more was caused by ghrelin release, which was most likely caused by DNA damage in skin cells from overexposure to sunlight. Oestrogen most likely prevented this in women. Researchers maintained that appetite regulation is a complex process that has a direct impact on health and involves the ghrelin and leptin8 hormones. Ghrelin levels are lowest after a meal and rise thereafter.
While music, light, and odour are environmental factors that influence ghrelin release, the underlying mechanisms remain unknown. ‘ These findings identify the skin as a major mediator of energy homeostasis and may lead to therapeutic opportunities for sex-based treatments of endocrine-related diseases,’ the researchers wrote in their paper.