New research suggests that weight impacts when and how bodies burn calories.

A recent study published in the journal Obesity from Oregon Health & Science University discovered that individuals with a healthy weight spend more calories during the daytime when they’re eating and most active, while individuals with obesity use more calories at night when most individuals are asleep.

Higher levels of insulin were also seen in those with obesity, according to the study. This is a signal that the body is struggling to use glucose.

According to the study's first author, Andrew McHill, Ph.D., an assistant professor in the OHSU School of Nursing and the Oregon Institute of Occupational Health Sciences at OHSU, "It was surprising to learn how dramatically the timing of when our bodies burn energy differed in those with obesity,".

McHill isn’t sure which came first, the chicken or the egg. “Burning less energy during the day could contribute to being obese, or it could be the result of obesity."

A BMI of 30 or higher is defined as having obesity. Being overweight or obese raises the risk of chronic diseases like high blood pressure and Type 2 diabetes.

Routines and when people sleep, eat, and get physical activity can also impact health by going against the body’s natural rhythms or working with them.

People experience multiple physiologic changes within 24 hours that are initiated by the body’s internal clock.

These changes normally happen at various times of the day so the body’s needs are best served at any time of day.

McHill and the study's senior author, Steven A. Shea, Ph.D., director of the Oregon Institute of Occupational Health Sciences at OHSU, focus their research on how circadian rhythms and sleep affect the human body.

The OHSU Sleep, Chronobiology and Health Laboratory is led by McHill.

Past research on how faulty circadian rhythms impact energy metabolism and regulation of glucose was primarily done in subjects who were at a healthy weight.

McHill, Shea, and colleagues explored this research further using participants of varying body sizes.

The small study included 30 volunteers and involved them staying at a specially designed circadian research lab for six days.

A rigorous circadian research protocol was used in the study. It involved a schedule designed to have participants be awake and sleep at different times during each day.

After each round of sleep, volunteers were woken up to eat and participate in various tests for the remaining time of each day.

Subjects were exposed to an indirect calorimeter, a test that measures exhaled carbon dioxide and helps estimate energy usage. This was done while exercising and wearing a mask.

Samples of blood were also collected to check glucose levels after an identical meal was given during the day.

Follow-up research will evaluate eating habits and hunger in people with obesity, as well as those with a healthy weight. That new research will follow from a 2013 study, done by Shea, that found circadian clocks naturally increase food cravings at night.

For clients trying to lose weight, sleep is good food! Below are tips for better sleep.

• Keep a sleep routine. Go to bed at the same time every night, even on weekends.

• Avoid eating at least three hours before bedtime.

• Get outside daily! Exposure to regular sunlight may improve the circadian rhythm.

• Limit screen time, especially at night. Turn off the TV, smartphone, or tablet.

• Reduce caffeine intake in the afternoon to prevent insomnia

• Adopt some form of regular physical activity (like walking) to reduce stress, burn calories, and improve sleep.

• Read, journal, or meditate before bed to relax your mind.

• Avoid alcohol at night. While it may help you get to sleep, it typically disrupts the sleep cycle.

• Skip the news and forgo emails late at night to reduce stress.

• Talk to your healthcare provider about low-dose melatonin or medication to help you get to sleep.

By Lisa Andrews, MEd, RD, LD

Reference:

1.    Andrew W. McHill, Saurabh S. Thosar, Nicole P. Bowles, Matthew P. Butler, Omar Ordaz‐Johnson, Jonathan S. Emens, Jonathan Q. Purnell, Melanie Gillingham, Steven A. Shea. Obesity alters the circadian profiles of energy metabolism and glucose regulation in humans. Obesity, 2023; DOI: 10.1002/oby.23940