Researchers from Jinan University and other institutes in China recently conducted a study on mice, exploring the possibility that bright light could reduce appetite and weight.
Previous research has shown that exposure to bright light and high levels of noise can modify both physiological processes and human behavior. For example, increased or, conversely, limited exposure to bright light and noise influences sleep patterns, circadian rhythm, mood, metabolism, stress levels, and mental performance. The new study shows that bright light also suppresses eating, as reported by Medical Xpress.
The current study, published in the journal Nature Neuroscience, has demonstrated that indeed, bright light reduces food intake in mice and can lead to weight loss.
"Environmental light regulates non-visual functions, such as feeding, and bright light therapy has anti-obesity potential, but its neural basis remains unclear. We show that treatment with bright light efficiently reduces food intake and limits weight gain in mice through a visual circuit involving the lateral hypothalamic area (LHA)," stated Wen Li, Xiaodan Huang, the study's author.
The Role of Light in Metabolism
It is already known that light plays an essential role in numerous physiological processes, such as sleep, hormone release, and eating patterns. Bright Light Therapy (BLT), which involves daily exposure to intense artificial light for at least 30 minutes, is already used in treating conditions such as seasonal affective disorder, insomnia, and depression.
Recent studies have indicated that BLT could facilitate weight loss or prevent excess weight gain. However, the neuronal mechanisms through which light influences eating behavior and body weight were not fully understood until now.
To investigate these mechanisms, scientists conducted an experiment on adult mice, dividing them into an experimental group and a control group. All mice were exposed to light for 12 hours a day and darkness for the remaining 12 hours. The difference was that, during the light period, mice in the experimental group were exposed to different light intensities, around 0, 1,000, 3,000, or 5,000 lux.
Researchers monitored the rodents' behavior and analyzed how light influenced their brain activity using chemogenetic techniques, methods that allow the control of activity in specific nerve cells through genetic modifications that make them sensitive to specific chemicals.
The results showed that mice exposed to bright light consumed less food and gained less weight. Additionally, a neuronal circuit responsible for this effect was identified, involving neurons from two different brain regions.
"Specifically, a subset of ON-type retinal ganglion cells expressing SMI-32 innervate GABAergic neurons in the ventral lateral geniculate nucleus (vLGN), which in turn inhibit GABAergic neurons in the LHA. Activation of both the retinal ganglion cells projecting to vLGN and the vLGN-LHA projection is sufficient to reduce food intake and diminish weight gain," explained the authors.