If you tend to eat most of your meals late in the day, your body might not be processing that food as well as it could. A new study from Germany finds that eating later in relation to your internal clock may impair glucose metabolism and that genetics may partly explain your eating patterns.
The study, published in eBioMedicine, followed 92 twins and found that those who ate closer to the end of their day (based on their natural sleep rhythms) had lower insulin sensitivity, a marker of how well the body regulates blood sugar. That effect was present even after accounting for total calorie intake, body weight and lifestyle habits.
Researchers used a concept called circadian timing of eating, which compares mealtimes to a person’s midpoint of sleep (a proxy for whether someone is an early bird or night owl). People who ate later relative to their sleep midpoint had poorer metabolic responses, even when diets were similar.
The twin design also helped researchers examine the role of genetics. Because identical twins share the same genes, while fraternal twins don’t, any consistent differences in eating behavior between the two can point to inherited influences. The study showed that genetics do seem to affect when people tend to eat, alongside lifestyle and cultural factors.
While previous research has linked late-night eating to higher risks of obesity and heart disease, this study adds clarity by tying it to a measurable shift in blood sugar control — one of the earliest steps toward type 2 diabetes.
The research was part of the NUGAT study and received support from the German Research Foundation, the European Association for the Study of Diabetes and Germany’s Federal Ministry of Education and Research. The work was also conducted within the German Center for Diabetes Research, which is funded by the Federal Ministry for Education and Research.