Well, this new article blew me away.
Research effected by Dr. Carmit Levy (Tel Aviv University, Israel), along with 36 coauthors, regarding the hormone called ghrelin provided new insights into our (male) behaviors. This hormone is produced (and released) by our stomachs.
It’s job? To let the brain know when the stomach is empty and we need to eat. Obviously, the levels of the hormone increase during mealtimes and drop dramatically when our stomachs are full. According to Dr. Levy, men and women manifest different behaviors from this hormone.
In the summer- when we are subject to sunny skies- men are induced to devour more calories. (Not in winter, when one would think it would be beneficial to stock up on comfort food.) And, you did see I said men- it’s not women who manifest this changed behavior.
The research is presented in their paper, Food-seeking behavior is triggered by skin ultraviolet exposure in males, published in Nature Metabolism. The study was examining mice and the mechanisms associated with skin cancer. That’s when the team found out that ultraviolet light exposure induced the males to devour more food.
The study then examined the responses of some 3000 folks who participate in Israel’s national health and nutrition survey. Surprisingly, they found that between March and September, men devoured 17% more calories a day than they did the rest of the year. (Women’s intake stayed relatively stable.)
This is how the team found that exposure to UV-B radiation (the wavelength present in sunlight) augmented the ghrelin secretion in the skin’s fat cells. This didn’t occur in women because their estrogen levels blocked the action.
They further examined this gender-based behavior. 27 folks (13 men) were exposed to 25 min of sunlight (2000 mJ/cm2 of U-B irradiation). Blood samples were taken 2/3 of day before and after the solar exposure and hunger feelings were examined among the subjects. Ghrelin excretion among the men- and their hunger feelings- were clearly elevated.
The team supposes that this adaptive response helps men become far more active (physically) in the summer. They don’t yet know if this hormonal response leads to weight gains during this “growing season”.
This is fascinating. But their conclusion that women’s calorie intake stays relatively consistent through the year, I’m not sure about that when it comes to me. In summer, I crave fruit and lighter fare. In winter, it’s heavier food – stews, heavy soups. It may be because of availability/price of certain foods, of course (who wants a winter tomato or watermelon, for example?)
And, perhaps because your estrogen levels have attenuated, Alana? Could that also so contribute to the changes?
Well this is interesting. Hubby is constantly hungry in the summer and when he’s doing more outside work. Hmmm
That could also be the result of physical activity, but the ghrelin action can’t be discounted.