What were the findings of randomized controlled trials on phototherapy—bright morning light—for weight loss?
If weakening our circadian rhythm can lead to weight gain, could strengthening it help with weight loss? Consider the child’s swing analogy mentioned earlier. Just as regular morning meals give our cycles a daily push, exposure to bright morning light provides the biggest shove. On the flip side, exposure to light at night could be likened to nighttime eating, as discussed further in my video Shedding Light on Shedding Weight.
Candles have illuminated our nights for millennia, but their light, skewed towards the red end of the spectrum, lacks the impact on circadian rhythms that blue wavelengths do. With the advent of electric lighting over a century ago, our exposure to blue wavelengths akin to morning sunlight has increased significantly, affecting our circadian rhythms profoundly.
Research using wrist meters showed that greater evening and nighttime light exposure was linked to a higher risk of obesity over time. This correlation, believed to be due to circadian misalignment, remained even after accounting for sleep duration in a study of over 100,000 women. Those sleeping in rooms with more light at night were significantly heavier, regardless of whether they used nightlights.
Without blackout curtains, neighborhoods with excessive light can disrupt circadian rhythms, leading to higher obesity rates. Excessive nighttime lighting has become so common that the Milky Way may soon only be seen on candy wrappers.
While sleep quantity can be controlled, sleep quality may be affected by nocturnal light exposure, impacting activity levels the next day. Randomized trials revealed adverse metabolic consequences in individuals exposed to bright light in the evenings or even for a single night.
The question arises: Can morning bright light therapy help with weight loss? Lack of morning light exposure could be similar to skipping breakfast. Exposure to morning light correlated with lower body weight compared to typical indoor lighting, prompting the use of “phototherapy” to address obesity. Initial case reports showed promising results, with some individuals losing weight over a short period.
Subsequent randomized trials indicated that bright morning light led to more significant body fat loss compared to standard indoor lighting, suggesting a potential link between light exposure and exercise motivation. The impact of light exposure on activity levels highlights its role in weight loss.
Further research explored the effects of morning bright light on weight loss, demonstrating possible benefits. Exposure to bright light could be a novel weight-loss strategy worth exploring.
For more information on chronobiology and weight loss, check out the related posts below or browse through the author’s weight loss videos.
Explore the full series on chronobiology and its impact on our health for a comprehensive understanding of environmental influences on our circadian rhythms.
Regardless of the mechanism, bright morning daylight exposure presents a unique weight-loss strategy.
