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Why do men eat more and gain weight in the summer and women don’t?

The role of the sun in human health is complex and not just related to the production of vitamin D. Men and women have different hormonal responses to environmental stimuli such as the sun. New research has shown that UVB from the sun’s rays can trigger the release of hormones in men, which encourages foraging behavior and increases their food intake. The same response has not been seen in women because estrogen blocks the hormonal pathway responsible for this behavior.

New scientific research has found that the sun can prompt men to forage and increase their food intake, while similar results have not been observed in women. This study, published in the journal Nature Metabolism, highlights the link between UVB, one of the sun’s invisible UV rays, and elevated levels of ghrelin, the “hunger hormone,” in men.

Ghrelin is a hormone that stimulates appetite, increases food intake, and promotes fat storage. It regulates energy, reduces nerve activity and prevents muscle wasting.

sun, health and sickness

The role of the sun and UVB exposure in human health is complex, but it is a recognized risk factor for the most serious forms of skin cancer: melanoma, actinic keratoses, premature aging and cataracts. However, the sun has also been shown to protect against heart disease, lower blood pressure and release mood-boosting endorphins. The beneficial effects of sunlight have often been attributed to vitamin D and its negative associations with UVB, but a recent study suggests the mechanisms may be more complex.

The new study, conducted by Tel Aviv University’s Department of Human Molecular Genetics and Biochemistry, showed that skin has a major impact on energy levels and suggests that this “leads to therapeutic opportunities for gender-specific treatments of endocrine disorders could. »

Different reactions

The researchers analyzed nutritional data from about 3,000 people aged 25 to 64 who participated in the National Health and Nutrition Survey (MABAT) over a 12-month period. According to the participants’ average monthly energy expenditure, men consumed an average of 300 kcal more during the summer months than women, whose calorie intake remained more constant (1,507 kcal vs. 1,475 kcal).

The researchers used a solar radiation experiment to better understand this difference. Five men and five women aged 18 to 55 were exposed to UVB for 25 minutes. The researchers drew blood before and after exposure and then analyzed it. The study showed that exposure altered proteins related to metabolism and that men and women responded differently.

The mechanism of weight gain

In another study, researchers used mice to study UVB exposure. Twenty-four partially shaved mice were exposed daily to a low concentration of UVB for 10 weeks. Mice showed similar metabolic protein changes as humans; male mice increased their food intake and foraging behavior. The researchers found that after UVB exposure, male mice showed increased release of the hormone ghrelin, which is specifically released by fat cells in the skin.

These results were confirmed in humans: the skin of men showed an increase in ghrelin expression after 5 days of UVB exposure. Studies have shown that DNA damage in skin cells was the trigger for the release of ghrelin via the p53 transcription pathway. Interestingly, the researchers found that this signaling pathway was blocked by estrogen, which could explain the differences between men and women.

Gender differences are very common when it comes to hormones and metabolic changes. Men and women have different hormonal responses to many different types of triggers, and the underlying hormonal balance is also different.

future research

If the study uncovered a potential mechanism for how UVB rays can affect hormone metabolism in both men and women, and how this might translate into increased ghrelin in mice, the researchers are by no means certain that sun exposure alone leads to weight gain in humans.

This is because age, genetics, activity level, and coexisting health conditions all affect hormone secretion. Much more research is needed to understand how we can use this information to help a person achieve and maintain a healthy weight. Still, this research clearly shows that men and women respond differently to seasonal changes, which can alter their metabolism significantly.

* Presse Santé strives to convey health knowledge in a language accessible to all. In NO CASE can the information given replace the advice of a doctor.

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