Leaving a two-hour gap between dinner and bedtime does not seem to be associated with any discernible difference in blood glucose levels among healthy adults, according to nurse researchers.
Avoiding eating a meal or snacking shortly before going to bed is generally thought to be better for long term health, noted the authors of the new study in Japan.
“Ensuring a short interval between the last meal of the day and bedtime did not significantly affect HbA1c levels”
It has been recommended for around a decade by the Japanese government that people leave a gap of two hours at least three times a week.
In Japan, 40-74 year olds get regular health checks, to try and lower the risk of lifestyle-related ill health, which increases with age.
This check includes a blood glucose test and an assessment of lifestyle and eating habits, such as whether people leave the recommended 2-hour gap between dinner and bedtime.
However, there is no clear evidence for the practice, said the researchers, so they chose to assess its potential impact on HbA1c levels.
The study, published in the journal BMJ Nutrition, Prevention and Health, was led by Dr Chiyori Haga, associate professor in community health nursing at Okayama University.
The researchers looked at health check data for 1,573 healthy middle-aged and older adults with no underlying conditions associated with diabetes in one city for the years 2012, 2013, and 2014.
Two thirds of the sample were women, and two thirds were over the age of 65 and retired.
As well as eating and drinking habits, the researchers looked at how much people smoked, their physical activity levels, and weight gain since the age of 20.
In all, 16% of the men and 7.5% of the women fell asleep within two hours of eating dinner, said the researchers.
Full data were obtained for 1531 adults for all three years. When HbA1c levels were higher to start with, these rose over time, but overall, it was gradual over the three years.
In addition, average HbA1c did not change significantly between 2012, when it was 5.2%, and 2013 and 2014, when it was 5.585, which is within the normal range.
Weight, blood pressure, triglycerides, physical activity, smoking and drinking seemed to be more strongly linked to changes in HbA1c levels rather than the interval between eating and sleeping.
As traditional Japanese diet contains a lot of vegetables and soup, and the portion sizes are small, the findings may not be wholly applicable to other nations, noted the researchers.
Nevertheless, they said: “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,” they said.