Artificial light at night or ALAN is causing serious concerns. As per studies, when there is chronic exposure to artificial light, the hormones are affected, and this could be the cause of the obesity epidemic which is worldwide. There are other studies conducted which show that artificial light exposure at nights results in hormonal cancers.
As per the Nara Medical school in Japan, 1100 elderly participants whose average age was 72, were followed for almost two years and their lifestyle, as well as health, was evaluated. It was found that those participants who had more exposure to artificial light gained more weight and increased in their waist size than those that did not have this artificial nighttime exposure to light. It was also seen that those who had exposure to natural light in the mornings had not only healthier body weight but also had smaller waist sizes. It was estimated that an increased night time light exposure increased the weight gain by 10.2 percent and the BMI increased by 10% over ten years.
The timing, as well as balancing of energy and the metabolism, is due to nerve cells which are called the suprachiasmatic nucleus and this is found in the hypothalamus. This is what is called the master biological clock. This sets the timing and the rhythm of the other clocks in the body which includes the thyroid, insulin, and leptin as well as the gene clocks too. Due to artificial light at night, the ambient light disrupts the rhythm of these internal clocks, and there is a misalignment created between the internal clocks in the body and the natural rhythm of the environment, and so this leads to decreased energy and impaired tolerance of glucose and so increase in obesity. As per the study, a sleep duration of about 5 hours a night reduces the insulin function by 20%.