Posted14 July 2022, 15:58
DiscoveryThe sun gives appetite to men but not to women
Scientists have surprisingly found that UV rays release a hormone that stimulates eating, but which is blocked by the female hormone estrogen.
UV rays cause fat cells in men’s skin to secrete an appetite hormone.
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Scientists never expected to find a link between skin and appetite. And it’s almost by chance that they did it. It was while studying the mechanisms of skin cancer that researchers at Tel Aviv University in Israel discovered that in mice, males exposed to UV (ultraviolet) light ate more .
To see if the same phenomenon was occurring in humans, the scientists went to consult data from the regular national survey of the eating habits of the Israeli population, involving around 3,000 people. They found that between March and September, men consumed 17% more calories per day than during the rest of the year, while this figure remained stable among women, writes the New Scientist.
Investigating why, and returning to mice, the scientists discovered that UV rays increased the secretion of a hormone called ghrelin by fat cells in the skin. This has also been seen in skin samples from UV-exposed men. Until now, it was thought that ghrelin was only secreted by our body when our stomach was empty. We discover that UV rays also play a role.
Fueling excess activity
Women do not have this effect because ghrelin is blocked by estrogen, the female sex hormone. It now remains to find the link between the sun and appetite. “It is not known why the effect occurs, but it may be an adaptive response to fuel greater physical activity in the summer, says Carmit Levy, author of the study published in «Nature Metabolism». The skin is the largest organ in the body, so it makes sense that this huge organ can sense the environment, sense that there’s UV at a time and now it’s time to get out.” As the article states, researchers have not studied whether or not this increased appetite for the sun is accompanied by weight gain in men.
