Eating during the day may reduce the risk for developing prediabetes and type 2 diabetes among night shift workers — a group that faces an increased diabetes risk — according to a new study published in the journal Science Advances.
Doing night shift work is a well established risk factor for type 2 diabetes, even though it’s often not mentioned along with more widely known risk factors like obesity, inadequate physical activity, and family history of diabetes. Scientists believe that the increased diabetes risk from doing night shift work is related to a mismatch between a person’s circadian rhythm — the body’s internal “clock” — and daily behaviors. On a deeper level, impaired glucose tolerance may happen when one key part of a person’s daily cycle — the rise and fall of body temperature throughout the day and night — doesn’t line up with another part, their glucose and insulin levels. Comparing these two daily cycles was the focus of the latest study.
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The study’s participants were 19 young, healthy people — 12 men and seven women — with an average age of 26.5 and an average body-mass index (BMI, a measure of body weight that takes height into account) of 22.7, indicating a normal or healthy body weight. Participants had an A1C level (a measure of long-term blood glucose control) ranging from 4.9% to 5.4%, indicating normal blood glucose levels (no one had diabetes). For 14 days, all participants underwent a carefully controlled study protocol in a laboratory, where they stayed for the duration of the study. First, participants had baseline measurements taken — including core body temperature, energy expenditure, and glucose and insulin levels — while staying awake for 32 hours in dim light. This was done to ensure that any effects seen from changes in meal timing, in the next phase of the study, could be compared with measurements in a constant state.
Next, participants underwent four 28-hour “days” of simulated night shift work — putting them 12 hours off from their sleep-wake cycle at the beginning of these “days.” Then, one group of 10 participants — the control group — continued to follow a 28-hour cycle with fixed mealtimes within those 28 hours. The other group of nine participants — the daytime meal intervention group — followed a 28-hour cycle for all behaviors except eating, which they did on a 24-hour cycle. This means that while their sleep schedule shifted from day to day, their eating always took place during the day.
Meal timing found to impact glucose levels
The researchers found that the timing of meals — either shifting along with sleep, or on a fixed daytime schedule — had no effect on core body temperature or energy expenditure. But it did have an impact on glucose levels over each 28-hour period. Participants in the control group saw their average glucose levels rise by 6.4% compared with before they began simulated night shift work. But participants in the daytime meal intervention group saw no increase in their average glucose levels compared with beforehand — meaning that daytime eating appeared to eliminate the typical glucose-raising effects of night shift work.
The researchers noted that the study participants were potentially not representative of actual night shift workers in several ways — they were young, healthy, didn’t take any medications, and didn’t have any sleep disorders. They were also given the opportunity to sleep in an optimum environment as part of the study — in a private, dark, quiet, temperature-controlled environment. Actual night shift workers might not have access to such an ideal sleep environment during the day, so it’s unclear in a number of ways how the study’s results would translate in to the real world. Still, they show that eating regularly during the day — regardless of shifts in your sleep schedule — might have a beneficial impact on glucose tolerance and reduce the risk for type 2 diabetes.