Regular sunbathing can act as a natural fat burner, study suggests.
Conventional wisdom says that people are less hungry on hot, sunny days, and now researchers have shown why.
Ultraviolet radiation reduces the levels of hunger hormones in the body, increasing appetite, but a simultaneous increase in the stress hormone norepinephrine increases the breakdown of fat and prevents weight gain.
It also causes white fat, which stores energy, to turn into brown fat, which burns energy, according to a new study in mice.
The researchers behind the study were so encouraged by their findings that they believe there might be a way to harness the benefits of UV rays in a way that doesn’t increase cancer risk to treat obesity.
Still, this is not an endorsement for running to a tanning bed or lying in the sun due to the high risk of skin cancer, including life-threatening melanoma.
Regardless of whether the mice were fed a normal diet (ND) or a high-fat diet (HFD), those exposed to UV light for 12 weeks did not gain significant weight.
While the study shows promise for UV therapies to treat obesity, researchers said this should not lead people to sit in the sun without proper protection or lie in tanning booths, which increases the risk of skin cancer. .
Dermatologists at Seoul National University Hospital in South Korea found that mice constantly exposed to ultraviolet radiation for 12 weeks, regardless of whether they were fed a normal or high-fat diet, did not gain weight.
Ultraviolet radiation caused an increase in levels of the neurotransmitter norepinephrine, which plays a crucial role in the body’s fight-or-flight response. Norepinephrine also helps regulate blood glucose levels.
Levels of the hormone leptin increased, which can lead to increased hunger because the body interprets it as a sign that it is lacking enough energy in the form of stored fat.
But rather than watching the animals gain weight, researchers found that when exposed to ultraviolet light, an increased release of norepinephrine caused the body to break down fat stores for energy, burning more calories without increasing physical activity. .
The ultraviolet light also caused adipose tissue to turn into brown fat, which burns energy to produce heat in the body.
Most of our body fat is white fat, which stores energy that the body uses to fuel basic metabolic processes and hard workouts. People with obesity have an accumulation of white fat.
Brown fat, for its part, produces heat in the body by burning energy reserves; The process begins when the body cools down to regulate body temperature.
Although the mice consumed more calories as their appetite increased, the body converted them into heat by converting white fat into brown fat before it could be stored under the skin, thus preventing weight gain.
The graph above shows changes in body weight in mice fed a normal diet. The red line represents those mice exposed to UV light, while the gray light represents mice that were not. Body weight was lower among those exposed to ultraviolet light
The graph shows changes in body weight among mice fed a high-fat diet. The red line represents mice exposed to UV light while on this diet, compared to mice that were not exposed to UV light, represented by the black line.
Dr. Jin Ho Chung, lead researcher and dermatologist at Seoul National University Hospital, said: This study clarifies the mechanism by which UV exposure can increase appetite and inhibit weight gain.
“In particular, the fact that ultraviolet radiation reduces leptin levels and increases norepinephrine, thus promoting the darkening of subcutaneous fat and increasing energy expenditure, provides an innovative clue for the development of obesity treatment strategies” .
Their discovery could pave the way for treatments that harness the benefits of UV exposure to mitigate weight gain, control blood sugar levels, and convert white fat into healthier brown fat.
He added: “This research demonstrates that UV exposure not only affects the skin but also plays a profound role in our body’s energy metabolism and homeostasis processes.”
This doesn’t mean that people should sit in the sun for hours at a time without sunscreen or sit in a tanning bed.
Ultraviolet radiation is known to damage the DNA of cells, which can build up over time and cause cells to grow out of control. This is a distinctive cause of cancer.
Dr. Dong Hun Lee, co-author of the study, said: “Since UV exposure can accelerate skin aging and promote skin cancer, it is advisable to minimize UV exposure and protect the skin with sunscreen”.
“Therefore, our research team plans to conduct follow-up studies to develop new strategies that can mimic the effects of UV radiation on obesity and metabolic regulation.”
His research was published in the Journal of Research Dermatology.
