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The Connection Between Light and Weight Loss

Date Aug 2023
Category health/lifestyle
Time reading 7 minutes
Man eating healthy

When it comes to managing weight, most of us are accustomed to the hard and exhausting balance of dieting and regular exercise. Not only that, but we spend most of our lives indoors under standard LED lighting. What does that have to do with weight?

Standard indoor lighting can actually affect our hunger levels and how effectively our metabolism works. Even though research shows that our modern habits can negatively affect our health, light can be the aid we need to help with weight management. That’s right, light can be the missing link. Light exposure and the timing of light exposure can be the difference between a healthy eating cycle and overeating.


The Link Between Light and Weight Management

Studies show an interesting correlation between light exposure, our body's internal clock (circadian rhythm), and weight management (McHill et al., 2017). These studies reveal that the timing of our meals, significantly influenced by light exposure, plays a pivotal role in our body's metabolism and weight regulation.

The researchers found that individuals with higher body fat percentages typically consumed a majority of their calories near the onset of melatonin release – our body's natural cue for sleep. It's not just the quantity or type of food we eat, nor physical activity levels that influence our weight; it's also our eating timing, significantly affected by light exposure, that plays a critical role.

It was also found that exposure to light-at-night might be a significant contributor to obesity. A study conducted by McFadden et al. (2014), which analyzed data from over 100,000 women, discovered that obesity odds increased with higher levels of light-at-night exposure, even when controlling for factors like sleep duration, alcohol intake, physical activity, and smoking.


Leptin and Ghrelin: Your Hunger Management System

Let’s talk about the two chemicals that control our hunger: leptin and ghrelin. Leptin tells our brain when we've eaten enough and should stop eating. It's released by our fat cells after we have a meal. So, when we finish eating, leptin levels go up and we feel less hungry. Ghrelin does the opposite. When we haven't eaten for a while, ghrelin levels increase, and it signals our brain that it's time to eat again. This makes us feel hungry and encourages us to find food.

After we eat, leptin tells us to stop eating, and when we haven't eaten for some time, ghrelin tells us to eat again. This cycle helps our body maintain a balance in the amount of food we consume. Irregular light exposure especially from indoor standard lighting may interfere with the normal production and release of leptin, which can lead to overeating.


Improper Light Exposure: A Hidden Culprit

Modern life is consumed with artificial lighting and digital screens that can keep us up hours late into the night. While this may seem harmless or even productive, it conflicts with our brain and bodies’ clocks, which remain anchored to the natural cycle of daylight and darkness (McHill et al., 2017).

If you’ve ever had the late-night munchies, it’s not your fault! It’s most likely that you have a circadian imbalance. When we’re influenced by our biology to eat food late into the night (a time our circadian rhythm traditionally reserves for sleep), it can lead to increased body fat and metabolic disturbances. Essentially, artificial light during nighttime disrupts the timing of our bodies’ systems, promoting an eating schedule that's out of sync with our biological requirements. Just another reason why we need to learn more about the relationship between light and our health!


Understanding Sleep and its Impact on Weight and Hormones

Think of your body as a complex machine. Your sleep pattern is driven by two main processes, the circadian rhythm (your body's internal clock) and sleep-wake homeostasis (balancing your need for sleep based on how long you've been awake), which controls the hormones that regulate everything from stress response to appetite.

For example, growth hormone (GH), well-known for cell regeneration and growth, gets supercharged during the deep, restorative stage of non-REM sleep, known as slow-wave sleep. When your sleep is out of tune, the GH performance can falter.

The same goes for cortisol, the 'stress hormone' that also plays a part in our metabolism. Its daily rhythm is tied closely to our sleep-wake cycle: sleep onset slows down its release, while waking up or sleep disruptions can rev it up.


Sleep, Glucose Regulation, and Metabolic Health

Our brain is an incredible organ, energy-hungry for glucose — think brain food — to function. The amount of this food it uses changes depending on whether you're asleep or awake.

Even when you're asleep and haven't eaten for hours, your brain's food supply, the blood glucose levels, stay pretty much the same or drop just a bit. It's like your body has its own smart storage system that makes sure the brain never runs low on food, even during the night. This smart system is your sleep at work.

But what does this mean for weight gain or loss, or for light dieting?

If you don’t get enough uninterrupted sleep, your body’s intricate balance might not work as it should. For instance, poor sleep can disrupt the hormones that control your appetite and how your body uses the food you eat. This could make you feel hungrier, lead you to overeat, or make it harder for your body to use that food efficiently—all of which can contribute to weight gain.


Connecting the Dots: Sleep, Obesity, and Metabolic Disorders

Now that you know the how of sleep, light, and weight connection, let’s dive a little deeper into why it’s important. Chronic sleep deprivation and disrupted sleep quality may even pave the way for obesity and type 2 diabetes. Studies show that sleep-deprived children and adolescents display stronger correlations between short sleep durations and obesity. We know that children need quality sleep to help them grow, but it goes even further than that. Insufficient sleep and sleep disorders may also impact the release of sex steroids and growth hormones during puberty, adding another layer of complexity to this issue.


Harnessing Light for Better Weight Management

While the research paints a concerning picture of modern habits and their impact on health, it also brings good news: we can wield light as an ally in our weight management journey.

A proper balance of natural light during the day and darkness at night can help align our mealtimes with our circadian rhythm, which could lead to more effective body composition management.

Proper light exposure can resynchronize our sleep-wake cycle and, by extension, our eating habits, to the natural day-night cycle.

In simpler terms, tuning our daily schedule to the cycle of the sun – being active and eating during daylight, while resting and fasting after sundown – can align our behaviors with our body's natural rhythm, fostering a healthier metabolism and promoting weight management.


Light Dieting for a Healthy Weight

Whether you're aiming to manage or lose weight, your relationship with light could be the missing piece of your performance puzzle.

The research provides a compelling argument for the influence of light on aligning our eating habits and weight management with a healthy circadian cadence. By strategically managing our light exposure, we can synchronize our mealtimes with our internal clock, making the path towards optimal health and performance feel more achievable and natural.

Imagine a world where you have complete control over your metabolic processes and your body works with you to achieve your weight goals.

That's the power of light dieting, a key factor in fine-tuning your weight management goals. You could be one sunset away from transforming your weight management journey.

The next time you reach for that late-night snack, remember to also assess your light exposure throughout the day. Have you had enough natural sunlight? Are you moderating your exposure to artificial light at night? These could be the performance-boosting insights you've been missing.



McHill, A. W., Phillips, A. J. K., Czeisler, C. A., Keating, L., Yee, K., Barger, L. K., Garaulet, M., Scheer, F. A. J. L., & Klerman, E. B. (2017). Later circadian timing of food intake is associated with increased body fat. The American Journal of Clinical Nutrition, 106(5), 1213–1219. DOI: 10.3945/ajcn.117.161588

McFadden, E., Jones, M. E., Schoemaker, M. J., Ashworth, A., & Swerdlow, A. J. (2014). The Relationship Between Obesity and Exposure to Light at Night: Cross-Sectional Analyses of Over 100,000 Women in the Breakthrough Generations Study. American Journal of Epidemiology, 180(3), 245–250. DOI: 10.1093/aje/kwu117

Leproult, R., & Van Cauter, E. (n.d.). Role of Sleep and Sleep Loss in Hormonal Release and Metabolism

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