Two-hour gap between dinner and bedtime may not affect blood glucose

Author: Ingrid Torjesen
Two-hour gap between dinner and bedtime may not affect blood glucose

Leaving a two-hour gap between the last meal of the day and bedtime doesn’t seem to be associated with any discernible difference in blood glucose levels among healthy adults over the long-term, suggests Japanese research* published in the online journal BMJ Nutrition, Prevention & Health.

Avoiding eating a meal or snacking shortly before going to bed is thought to be better for long-term health, and in Japan it is recommended that people leave a two-hour gap at least three times a week.

In Japan, 40-74 year olds get regular health checks, which include a blood glucose test and an assessment of lifestyle and eating habits, such as whether people leave the recommended two-hour gap between dinner and bedtime. However, the researchers say there is no evidence to support this gap, so they decided to assess its potential impact on HbA1c levels, which are considered an indicator of future health risks.

They analysed health check data for 1573 healthy middle-aged and older adults with no underlying conditions associated with diabetes for 2012, 2013, and 2014. Two-thirds of the sample were women, and two-thirds were over the age of 65 and retired. In all, 83 (16%) of the men and 70 (7.5%) of the women fell asleep within two hours of eating dinner.

Full data were obtained for 1531 adults for all three years, and these showed that when HbA1c levels were higher to start with, these rose over time. Average HbA1c didn’t change significantly between 2012, when it was 5.2%, and 2013 and 2014, when it was 5.58%, which is within the normal range. There were no significant differences in levels between men and women.

Weight (BMI), blood pressure, blood fats (triglycerides), physical activity levels, smoking and drinking seemed to be more strongly associated with changes in HbA1c levels rather than the interval between eating and sleeping, the findings showed.

The researchers point out that the traditional Japanese diet contains a lot of vegetables and soup, and the portion sizes are small, so the findings might not be applicable to other nations. However, they conclude: “Contrary to general belief, ensuring a short interval between the last meal of the day and bedtime did not significantly affect HbA1c levels.

“More attention should be paid to healthy portions and food components, getting adequate sleep and avoiding smoking, alcohol consumption, and overweight, as these variables had a more profound influence on the metabolic process.”

*Maw SS, Haga C. Effect of a two-hour interval between dinner and bedtime on glycated haemoglobin levels in middle-aged and elderly Japanese people: a longitudinal analysis of three-year health check-up data. BMJ Nutrition, Prevention & Health 2019;bmjnph-2018-000011. doi: 10.1136/bmjnph-2018-000011