Obese People Consume More Energy at Night

A recent study conducted by Oregon Health and Science University (OHSU) and published in the journal Obesity has shed light on the energy consumption patterns of individuals based on their weight. The research revealed that individuals with a healthy weight tend to consume more energy during the day, when they are most active and engaged in eating. Conversely, obese individuals tend to consume more energy at night, during the sleeping hours. Additionally, the study found that obese individuals exhibit higher levels of the hormone insulin during the day, indicating increased efforts by their bodies to utilize glucose, a sugar rich in energy.

Dr. Andrew McHill, the study's lead author and an assistant professor at the OHSU College of Nursing, expressed surprise at the discrepancy in how energy is burned in obese individuals but was uncertain about the underlying reasons.

Obesity is defined as having a body mass index (BMI) of 30 or above. Being overweight or obese elevates the risk of various health conditions, including high blood pressure and type 2 diabetes.

The timing of sleep, meals, and physical activity also plays a crucial role in overall health, either supporting or disrupting the body's natural daily rhythms. Within a 24-hour cycle, the body undergoes numerous changes regulated by its internal biological clock. These changes typically occur at specific times of the day to best align with the body's requirements at any given moment.

Dr. McHill and the study's senior author, Dr. Steven A. Shea, who is the director of the OHSU Institute of Occupational Health Sciences, focused their research on investigating how circadian rhythms and sleep impact the human body. Dr. McHill helms the OHSU Sleep, Chronobiology, and Health Laboratory.

Previous studies have demonstrated the influence of circadian rhythm dysregulation on energy metabolism and glucose regulation, but these investigations primarily involved participants with a healthy weight. To delve deeper into this topic, Dr. McHill, Dr. Shea, and their colleagues conducted a study encompassing individuals with varying body types. Thirty volunteers participated in this research, spending six days in a specially designed circadian rhythm research laboratory. The study adhered to a strict circadian rhythm protocol, incorporating a schedule that manipulated participants' waking and sleeping times.

Following each sleep period, the volunteers were awakened to consume meals and partake in various tests throughout the day. One such test involved participants exercising while wearing masks connected to an indirect calorimeter, a device that measures exhaled carbon dioxide to estimate energy expenditure. Blood samples were also collected from participants to monitor blood sugar levels after consuming identical meals each day.

Moving forward, the research team intends to investigate the eating habits and appetite of both obese and normal-weight individuals. A 2013 study led by Dr. Shea revealed that the body's internal clock naturally increases cravings for food during nighttime.