Poor sleep and inconsistent sleep schedules that go against the body’s biological clock negatively affect the body’s metabolism by increasing the risk for developing obesity and diabetes, according to a new study.

While previous studies have also found a connection between sleep patterns and diabetes and metabolic syndrome risk, especially in night-shift workers, unlike past studies that were either short-term or observational, researchers actually controlled the lives of 21 people in the study, including the meal and bedtimes. 

The findings, published in Science Translational Medicine, show that participants who were put on more shift-like sleep schedules developed poorer glucose regulation and metabolism, and scientists explained that over time the heightened risk of obesity and diabetes was apparent. 

"We think these results support the findings from studies showing that, in people with a pre-diabetic condition, shift workers who stay awake at night are much more likely to progress to full-on diabetes than day workers," study researcher Dr. Orfeu Buxton, a neuroscientist at Brigham and Women's Hospital, said in a statement.

"Since night workers often have a hard time sleeping during the day, they can face both circadian disruption working at night and insufficient sleep during the day," Buxton added. "The evidence is clear that getting enough sleep is important for health, and that sleep should be at night for best effect."

All of the participants in the study spent 21 days before the experiment with consistent bedtime and 10 hours in ben each night as well as normal exposure to daylight.

In the experiment, researchers put each participant in an individual suite for 39 days in dim light and without time cues.  All participants spent 16 hours a day in bed, sleeping as much as they wanted for the first 5 days of the study.

Afterwards participants were put on restricted sleep schedules for three weeks.  Participants had no more than 5.6 hours of sleep in a in 24 hour periods, and all participants were put on different sleep/wake and feeding/fasting periods based on a 28-hour “day”.

After the three weeks had past, researchers put participants on 9 days of "circadian re-entrainment," in which participants received a consistent 10 hour bedtime every 24 hours. 

Researchers then measured participants’ body weight, resting metabolic rate and metabolic responses to a standardized meal, and found that a combination of little sleep and circadian rhythm disruption significantly decreased insulin secretion after the meal.

During fasting periods insulin concentration dropped by an average of 12 percent, after meals and integrated plasma insulin concentration both dropped substantially by an average of 27 percent, which led to significant increases in fasting as well and after peak plasma glucose concentrations compared to levels from the start of the study. 

Fasting concentrations had risen overall by an average of 8 percent after-meal concentrations, after-meal concentrations by 14 percent and the integrated postprandial response over 90 minutes increased by 15 percent, which would translate into a yearly weight gain of approximately 10 pounds if diet and physical activity stayed the same, according to the authors. 

Researchers reported that most of the changes returned to normal or near-baselines levels during the nine-day recovery phase of the experiment. 

Previous research published in the journal Immunity also found that a disrupted body clock weakened the immune system, putting the body at risk for more infections. 

Researchers at Yale School of Medicine found that the circadian clock controls the activity of key Toll-like receptor 9 that responds to the presence of DNA from bacteria and viruses, in mice.

Study author Erol Fikrig, professor of epidemiology and microbial pathogenesis, said that although people have intuitively known that they when their sleep patterns are disturbed they are more likely to get sick, and now the study findings appears to give evidence that “disruptions of the circadian clock influence” does in fact increase the “susceptibility to pathogens”.

Researchers said that that jet lag may directly contribute to infections or illnesses when traveling, and also that there may be better times in the day to get vaccinated.