The body's metabolism works differently throughout the day, with many functions peaking in the morning and tapering off in the evening. While previous research has linked late eating to an increased risk of obesity and cardiovascular disease, the specific impact of meal timing on glucose metabolism and the role of genetic factors remain unclear.To explore this further, Professor Olga Ramich and her team at the Potsdam-Rebrück Institute of Human Nutrition (DIfE) in Germany conducted a study on twins. Their findings were recently published in"eBioMedicine》 magazine.

The circadian system is a complex network of internal clocks that follow a 24-hour rhythm. A central clock in the brain coordinates behavior and metabolism, while other peripheral clocks operate in organs such as the liver and pancreas. This system causes the body's metabolic activity to fluctuate based on meal times, affecting blood sugar regulation and hormone release. Mealtime is a key signal for adjusting these internal clocks. However, when eating habits deviate from the body's natural circadian rhythm (such as among shift workers), circadian rhythm disruption may occur and may lead to metabolic problems.

Early research has established a link between late-night eating and increased risk of obesity and cardiovascular disease.

However, it remains unclear how meal timing is coordinated with the body's internal circadian rhythm and how this coordination affects glucose metabolism and the likelihood of developing diabetes. Furthermore, the factors that influence individual dietary patterns remain unclear because they are the result of a complex combination of cultural, personal, physiological, and genetic factors.

The time of day you eat affects glucose metabolism and insulin sensitivity. Photo credit: David Ausserhofer/DIfE

In this context, Heisenberg Professor Olga Ramich of the Charité Universität Berlin and the Potsdam-Rebrück Institute of Human Nutrition (DIfE) in Germany explored the relationship between daily eating timing and glucose metabolism and insulin sensitivity. Ramich is also collaborating with the German Diabetes Research Center (DZD), where she and her team aim to identify the genetic and environmental factors that influence individual dietary patterns.

The researchers used data from the Nutrigenomics Analysis of Twins (NUGAT) study, which involved 46 pairs of identical and fraternal twins who did not have diabetes. Participants kept detailed food diaries for five consecutive days, recording the timing and quantity of meals eaten. The research team assessed each person's sleep-wake cycle (circadian clock) and performed multiple metabolic assessments, including a glucose tolerance test. In addition, they calculated the circadian rhythm of food intake, meaning they analyzed each person's meal times in relation to their internal body clock, rather than just body clock time.

An important parameter that the scientists determined was the subject's circadian caloric midpoint (CCM). CCM describes the point in the day when 50% of daily calories are consumed. Therefore, later CCM means that a person eats primarily later in the day, which is related to the type of body clock the individual has.

"People who eat their main calories earlier in the day have higher insulin sensitivity," explains Ramich, Head of the Department of Molecular Metabolism and Precision Nutrition at DIfE. "On the other hand, subjects who consumed their main caloric intake later in the day had poorer insulin sensitivity, which is associated with a higher risk of type 2 diabetes." In addition, they also had higher body mass index (BMI) and waist circumference.

To explore the influence of genes on eating timing, researchers compared the eating behavior of identical twins (who are 100% genetically identical) and fraternal twins (who are about 50% genetically identical). Using special mathematical models, they estimated the extent to which eating timing is affected by genes, shared environment or personal experiences.

Research shows that various parameters of daily dietary patterns are influenced by genes by up to 60%.

Advancing major caloric intake to circadian timing may improve glucose metabolism and prevent type 2 diabetes and obesity. "However, because eating timing is partly influenced by genetics, some people may have difficulty changing their habits," Ramich noted. "Further validation studies and clinical trials are needed to better understand the effectiveness of mealtime-based interventions."

By measuring the time between a person's eating time and the midpoint of their sleep, it is possible to assess the relationship between a person's eating time and their internal biological rhythms. This midpoint refers to the halfway point between falling asleep and waking up. It can serve as an indicator of a person's type of body clock, indicating whether a person is more active in the morning or evening.

The NUGAT study was initiated and designed by Professor Andreas FH Pfeiffer and was conducted from 2009 to 2010 at the Potsdam-Rebrück Institute for Human Nutrition (DIfE) in Germany. Monozygotic and dizygotic twins were recruited from the Twin Registry (HealthTwiSt, Berlin, Germany) or through public advertisements. Ninety-two participants (46 twin pairs) received two nutritional interventions, but these interventions were not associated with study outcomes.

Participants underwent detailed metabolic phenotyping, including physical examination, medical history taking, anthropometric measurements, and glucose tolerance testing. An individual's sleep type is determined through a questionnaire. In addition, all 92 test subjects filled out handwritten food logs, recording the start and end times of each meal, as well as intake and food types for five consecutive days. The five days included three working days and two rest days to reflect the twins' eating habits.

Compiled from /scitechdaily