• A study in overweight individuals concludes that misaligned body clocks are associated with raised metabolic risk factors.
• The findings show these metabolic changes vary between males and females.
• Realigning the body clock with sufficient sleep could help reduce the negative health implications of overweight and obesity, researchers say.

Circadian rhythms are 24-hour cycles that the body goes through each day — an internal “body clock.” These cycles include fluctuations in levels of hormones and neurotransmitters and drive the daily sleep-wake cycle.

A recent study from researchers at Oregon Health & Science University (OHSU) shows that people with overweight or obesity whose circadian rhythms are poorly aligned may experience negative metabolic effects.

The findings, published August 20 in The Journal of Clinical Endocrinology & Metabolism, suggest these negative effects vary significantly between males and females.

Readjusting the body clock could potentially reduce some of the risks associated with overweight and obesity, researchers say, although more evidence is needed to determine these effects.

How does overweight or obesity affect sleep?

Scientists have known for many years that getting enough good quality sleep is essential for good health. However, many people in our modern society are getting fewer hours of shuteye than ever.

Research has also shown a close relationship between inadequate sleep and weight gain.

For instance, the authors of a review on the subject concluded that short sleep duration was significantly associated with the risk of developing obesity in the future, but that long sleep duration was not. Research also suggests that circadian misalignment may be linked to increased energy intake and obesity risk.

Jacob Teitelbaum, MD, a board-certified internist and expert in chronic fatigue syndrome, fibromyalgia, sleep, and pain, explained why circadian rhythms are so important.

“The circadian rhythm is the critical ‘orchestra conductor’ for your body,” he told Healthline. “It regulates the proper timing of your hormonal and immune systems, and numerous other functions.” Teitelbaum was not involved in this study.

Studies have shown that circadian misalignment — which could mean feeling awake while the internal body clock is promoting sleep or eating when the body should be sleeping — is associated with less energy expenditure during the day.

In other words, people in this misaligned state burn fewer calories. Not sleeping enough is also linked to consuming more calories throughout the following day.

The relationship is complex, though, and researchers are still trying to understand precisely how body clock misalignment and insufficient sleep impact metabolic health.

What’s the relationship between circadian rhythm and obesity?

In the latest study, the scientists recruited 15 females and 15 males, all with overweight. They measured their body composition and took blood samples.

They also assessed their dim-light melatonin onset (DLMO). Melatonin is an important hormone that helps maintain circadian rhythms. As the day draws to a close and light levels fall, the brain produces melatonin. As levels increase, the individual becomes increasingly sleepy.

DLMO measures when melatonin release begins in dimly-lit conditions. Because melatonin release is a sign that the body clock is preparing an individual for sleep, scientists use DLMO as a marker of circadian rhythm phase.

By measuring the time difference between melatonin beginning to rise and the participant going to sleep, the researchers gauged the level of circadian rhythm misalignment.

Study co-author Brooke Shafer, PhD, a postdoctoral researcher with the Sleep, Health, & Chronobiology Laboratory at OHSU Portland Campus School of Nursing explained why this is important:

“Your body has a time that it starts to signal the brain to fall asleep, and if we try to sleep really close to that time, we may have trouble sleeping or have a lower quality sleep,” Shafer told Healthline.

Following the week-long study, the researchers identified sex-specific effects of body clock misalignment.

Misaligned males had:

• higher levels of abdominal fat
• higher levels of blood fat (triglycerides)
• a greater risk of metabolic syndrome

Misaligned females had:

• a higher percentage of overall body fat.
• higher blood sugar levels.
• a higher resting heart rate.

Shafer shared that she was surprised by the sex differences. “These findings really emphasize that there is no one-size-fits-all approach to maintaining healthy behaviors,” she said.

In particular, she explained, “the sex-specific differences in how sleep habits affected glucose and triglyceride levels were quite notable.”

This is important because individuals who have high levels of blood fat or blood sugar have an increased risk of heart disease.

These findings suggest that “circadian disruption may not only promote a trajectory of weight gain but could also contribute to negative health consequences in a sex-dependent manner in those already with overweight/obesity,” the study authors wrote.

The researchers hope that optimizing circadian alignment could help reduce the risk of poorer health outcomes, particularly in people with overweight or obesity.

Shafer said the team will continue to study the impact of circadian rhythm misalignment.

“Our next steps are to look at sex-specific differences in health markers for individuals who are vulnerable to extreme sleep disturbances, such as those who work during nighttime hours,” she said.

How to realign circadian rhythm

The current study is small-scale, so scientists need to carry out more work to confirm the results. However, a number of studies have shown that a misaligned body clock is linked to negative health outcomes.

The good news is that most people can readjust their body clock with good sleep habits.

This could mean that an individual with overweight might be able to reduce their risk of metabolic diseases by working to realign their circadian rhythms. However, trying to maintain a healthy weight should still be the primary goal.

Chelsea Perry, PhD, owner of Sleep Solutions in Westborough, MA, not involved in the study, and member of the American Academy of Sleep Medicine, suggested the following tips to for getting your internal body clock back on track:

• Maintain a consistent sleep schedule, even on weekends.
• Get exposure to natural light, especially in the morning.
• Limit screen time and bright lights in the evening. This helps signal to your body that it is time to wind down.
• Gradually adjust your bedtime and wake time by 15–30 minutes each day to help ease your body back into its natural rhythm.

Cherilyn Davis, MD, a board-certified pediatrician with Elliston Pediatrics, likewise not involved in the study, offered additional tips to optimize sleep:

• Avoid things that may disrupt sleep, like drinking caffeinated drinks before bedtime.
• Make your sleeping space comfortable, cool, and dark.
• Avoid napping or exercising late in the day, as this may make you less tired at night and disrupt circadian rhythm.

Takeaway

A new study concludes that people with overweight and have a misaligned body clock may be at a greater risk of metabolic disease. Conversely, the authors hope that realigning circadian rhythms might help reduce these risks.