This article investigates how sex differences matter when studying sunlight and hunger. There were studies that indicate that sunlight has the potential to treat obesity. But, now, new research has found that sunshine can cause men hungrier (while women are unaffected). This recent study that came out in the journal Nature Metabolism highlights the relationship between UVB and elevated levels of ghrelin (hunger hormone) in males.
By the way, UVB is one of the types of invisible ultraviolet rays that come from the Sun. UVB rays, short for ultraviolet B rays, are a type of ultraviolet (UV) radiation emitted by the sun. They are part of the electromagnetic spectrum and have shorter wavelengths than UVA rays but longer wavelengths than UVC rays. Remember, UVB rays are one of the main factors responsible for causing sunburn and are considered more harmful than UVA rays.
We know that sex differences have a profound effect on health and behavior. But whether male-female differences are important to environmental cues such as ultraviolet (UV) radiation remains underinvestigated. This new study at the Department of Human Molecular Genetics and Biochemistry at Tel-Aviv University is an ambitious step in this direction.
The research team analyzed the dietary data of about 3000 people aged between 25 and 64 over a period of 12 months and examined sunlight and hunger relations. They found that men eat an average of 300 kcal more during summer months while women participants eat only 32 kcal more during the same period.
Then researchers employed a solar exposure experiment to shed more light on their findings. Five men and five women were exposed to UVB for 25 minutes, with a sampling of blood before and after the exposure. The researchers found that male skin showed an increase in ghrelin expression for 5 days post-UVB exposure.
In another study, the research team conducted the same UVB exposure experimented on mice. Twenty-four mice (partly shaved) were exposed daily to low levels of UVB. They found similar results to that of humans. Male mice increased their food intake due to the increased release of ghrelin hormones.
Though the study has revealed how UVB rays can affect human metabolism in men and women, the result is far from claiming that sunlight exposure will result in weight gain in humans.