We already know the main external factors that increase the risk of obesity: lack of physical activity, a high-calorie diet, stress, and sleep quality. But a new study has gone further on this last factor: the impact of light on weight gain.
According to the researchers, turning off the television and cutting yourself off from all artificial light sources at bedtime is the best thing to do to reduce the risk of gaining weight.
Sleeping with the TV on = 1 stone more
To assess this criterion, the researchers interviewed 43,722 women and measured their weight, height, waist, and hip circumference. The participants were aged between 35 and 74 years and did not have any lifestyle habits that could influence the study, such as sleeping during the day or being employed in shift work. The survey asked the participants whether they sleep with any light sources nearby.
The results allowed the researchers to deduce the impact of artificial light on weight gain. For example, while the use of a small nightlight had no significant impact, falling asleep near a lamp or television had a 17% greater chance of gaining 1 stone. The presence of light from another room, on the other hand, had no obvious effect.
How does this work?
During sleep, a hormone is naturally produced by the human body: melatonin, the release of which influences the body's biological mechanisms, and which is largely dependent on light, as Dr Chandra Jackson, co-author of the study, explains:
Humans are genetically accustomed to the natural light changing between day and night. Exposure to artificial light disrupts body function and increases the risk of health problems such as obesity.
City dwellers more at risk
In addition to reducing light sources in the home, the co-author points out that people living in cities are more exposed to artificial light, whether from neon lights in shops, building lights, or signage. This finding could present city lights as a public health problem, as well as an environmental problem. It should be noted, however, that this study focused exclusively on a sample of women. Further scientific research is needed to confirm, or discredit, this trend in men.