What does going to bed later do to your blood sugar and insulin?

Going to bed later than your body is used to disrupts how your blood sugar is processed after eating. Smaller studies show that a shift of at least two hours, while keeping total sleep time the same, leads to less favourable blood sugar levels in half of the measured situations, particularly after meals. In the other half, no measurable difference was found. Fourteen of the sixteen studies involved fewer than two hundred participants combined, so this picture is still preliminary.

People who consistently sleep at unusual times, such as night or shift workers, face greater risks over the long term. The more years spent doing shift work, the greater the chance of disrupted blood sugar, reduced sensitivity to insulin, and eventually type 2 diabetes. This pattern has been found repeatedly among healthcare workers. Whether it is caused entirely by shifted sleep times, or also by lack of sleep and stress, has not yet been fully established.

In pregnant women, a late sleeping and eating pattern is linked to a higher risk of gestational diabetes. If you are pregnant and notice that you consistently eat and go to bed late, it is worth discussing this with your midwife or doctor.

Your internal body clock is also rooted in your genes. Certain variants in body-clock genes are associated with higher blood sugar levels and a greater chance of type 2 diabetes, as shown in more than 535,000 people. Other body-clock gene variants are associated with slightly lower insulin levels and a reduced diabetes risk. So your genes do not all steer your internal clock in the same direction.