The Role of Light in Regulating Hunger and Satiety

Sunlight exposure during the day

1. Regulation of circadian rhythm:
   • Natural light, in particular the blue light of the sun, stimulates the photoreceptors in the eye that communicate with the hypothalamus (specifically the suprachiasmatic nucleus, or SCN), our “biological clock”.
   • This signals to the body that it is daytime, synchronizing the circadian rhythms with the natural cycle of light and darkness.
2. Production of serotonin:
   • Sun exposure stimulates the production of serotonin, a neurotransmitter that promotes good mood and feeling of well-being.
   • Serotonin is a precursor of melatonin, the sleep hormone, which is produced when light decreases.
3. Improvement of mood:
   • Exposure to sunlight is associated with a reduction in the risk of seasonal affective disorder (SAD) and improved overall vitality.
4. Metabolic regulation:
   • Sunlight helps regulate hormones that affect metabolism and energy expenditure.

 

Reducing light exposure in the evening

1. Increased melatonin production:
   • The decrease in light exposure, especially blue light (emitted by screens and LED lamps), allows the body to start producing melatonin, which promotes deep, restorative sleep.
2. Reduction of cortisol:
   • A decrease in exposure to light signals the body to lower cortisol levels, the stress hormone, promoting relaxation.
3. Improved sleep:
   • Sleeping in a dark environment improves sleep quality, positively affecting memory, learning, cell regeneration and immune health.

Effects on hunger and satiety mechanisms

1. Regulation of appetite hormones:
   • Circadian rhythms influence the production of ghrelin (the hunger hormone) and leptin (the satiety hormone). A misaligned circadian rhythm can cause disruptions that increase the feeling of hunger and reduce satiety.
   • A good circadian balance improves the body’s response to hunger and satiety signals, reducing the likelihood of overeating.
2. Reduced nighttime cravings:
   • Excessive exposure to artificial light in the evening can alter the circadian rhythms, increasing the likelihood of seeking foods rich in sugar and fat at night.
3. Synchronization of metabolism:
   • Metabolism follows a circadian rhythm, with digestion and nutrient absorption working most efficiently during the day. Exposure to natural light helps the body regulate its energy use more effectively.

 

Other general benefits

• Support for vitamin D synthesis: indispensable for strong bones, immune system and cardiovascular health.
• Reduced risk of chronic diseases: well-regulated circadian rhythms are associated with a reduction in the risk of obesity, type 2 diabetes and cardiovascular diseases.
• Improvement of cognitive performance: a good regulation of the circadian rhythm optimizes attention and concentration during the day.

 

Practical advice

1. Sun exposure in the morning:
   • Spend at least 20-30 minutes in the sun, preferably shortly after waking, to adjust the circadian rhythm.
2. Avoid artificial light in the evening:
   • Turn off or reduce intense lighting after sunset, use warm lighting and set night modes on screens.
3. Create a dark environment for sleep:
   • Use blackout curtains and turn off light sources in the bedroom.
4. Follow a regular schedule:
   • Keep regular meal and sleep times aligned with the natural day-night cycle.

These habits can significantly contribute to overall well-being, improving both physical and mental health.