Effects of the Internal Circadian System and Circadian Misalignment on Glucose Tolerance in Chronic Shift Workers
Summary
This randomized crossover study tested how circadian timing and circadian misalignment affect glucose tolerance in chronic shift workers. In tightly controlled lab conditions, workers ate identical meals during their biological morning and evening, both with and without circadian misalignment. Results showed that blood sugar control was 6–7% worse in the biological evening compared to the morning, and that circadian misalignment independently worsened glucose tolerance by about 6%, even with the same sleep, food, and activity schedules. The impairments were tied to weaker insulin secretion in the evening and reduced insulin sensitivity under misalignment.
Why It Matters For Night Shift Workers and Night Owls
This study shows that your body’s ability to handle food depends strongly on when you eat. Blood sugar regulation works best in the biological morning, while eating in the biological evening or during circadian misalignment leads to higher glucose spikes. For night-shift workers, this means that meal timing is as important as meal content. Keeping larger meals earlier in the day and minimizing heavy overnight eating may help reduce long-term risks like diabetes that are linked to night-shift work.