If you pride yourself on staying up late to watch TV or catch up on reading and other tasks, you might want to flip your schedule a bit.
New research suggests that night owls may be more likely to develop heart disease or diabetes than early birds. People who get up early in the morning seem to burn more fat as an energy source and are often more active than those who stay up late.
That’s according to a study in the journal Experimental Physiology. Researchers from Rutgers University found that those who get up early use more fat during both rest and exercise, regardless of their aerobic fitness, compared to the late-to-bed folks. The former are also more active throughout the day, using more fat, while their late-night counterparts tend to store more.
While the two groups were similar in body composition, the early risers were more sensitive to insulin blood levels and they burned more fat while they were exercising and resting. Instead of burning fat for fuel, the study found that night owls used carbohydrates for energy.
Steven Malin, a professor at Rutgers who led the study, told The Guardian that his team had not decoded why the two groups of people had metabolism that worked differently. He said it could be a “mismatch” between the time people go to bed and wake up, and their natural circadian rhythms.
“Night owls are reported to have a higher rate of obesity, Type 2 diabetes and cardiovascular disease when compared to early birds,” he said. “A potential explanation is they become misaligned with their circadian rhythm for various reasons, but most notably among adults who work.”
He noted that night owls might still have to go to work in the morning, so they get up early. That could disrupt their natural body clock. CNN noted that people who are chronically misaligned with their body clock are said to have “social jet lag.”
“The study adds to what we know,” Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University and not involved with the study, told CNN. “There is good evidence that being a late sleeper has been linked to a higher risk for metabolic and cardiovascular disease.”
Zee noted that “several mechanisms have been proposed: sleep loss, circadian misalignment, eating later in the day and being exposed to less morning light and more evening light, which have all been shown to affect insulin sensitivity.”
The article said night owls are more likely to engage in risky behavior and use more tobacco, alcohol and caffeine. They also often skip breakfast, but load up on food later in the day.
The study sorted 51 adults who don’t have diabetes or heart disease by whether they would fall into the early bird or night owl category. Each had a restricted diet and fasted overnight. Their activity level was also monitored for a week. Their body mass index, fitness level and body composition was also noted, as well as their insulin sensitivity measured.
The news doesn’t always favor early birds.
In 2009, Science reported, “Two factors control our bedtime. The first is hardwired: A master clock in the brain regulates a so-called circadian rhythm, which synchronizes activity patterns to the 24-hour day. Some people’s clocks tell them to go to bed at 9 p.m., others’ at 3 a.m. The second factor — called sleep pressure — depends not on time of day but simply on how long someone has been awake already.”
The study from Belgium found that “those who go to bed late outperform early birds on some cognitive tasks,” Science said, including some requiring attention and speed. The article called it a “result with real-world consequences,” according to sleep researcher David Dinges of the University of Pennsylvania School of Medicine in Philadelphia.
“Current risk analyses use the time of day and hours worked to predict when people are in greatest danger of accidents — such as aviation errors,” that article said. “But now, Dinges says, they may need to take into account that morning people tend to lose their concentration faster. At the very least, according to sleep researcher Amita Sehgal, also at the University of Pennsylvania School of Medicine, this is a new and ‘intriguing’ explanation for larks’ and owls’ different habits.”