Late-Night Eating Linked to Obesity, Heart Disease
The body’s metabolism operates differently throughout the day, with many functions reaching peak activity in the morning and slowing down by evening. While prior research has linked late-day eating to higher risks of obesity and cardiovascular conditions, the specific impact of meal timing on glucose metabolism and the role of genetic factors remain unclear. Their findings were recently published in the journal eBioMedicine.
To explore this further, Prof. Olga Ramich and her team at the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE) conducted a study involving twins.
The circadian system is a complex network of internal clocks that follows a 24-hour rhythm. A central clock located in the brain coordinates behavior and metabolism, while additional peripheral clocks operate in organs like the liver and pancreas. This system causes the body’s metabolic activity to fluctuate depending on when food is consumed, influencing both glucose regulation and hormone release. Mealtimes act as key signals that align these internal clocks. However, when eating patterns stray from the body’s natural light-dark cycle—as seen in shift workers—circadian disruption can occur, potentially leading to metabolic problems.
Earlier research has established a link between late-night eating and a heightened risk of obesity and cardiovascular conditions.
Yet the precise ways in which meal timing aligns with a person’s internal circadian rhythm—and how this alignment affects glucose metabolism and the likelihood of developing diabetes—are still not well understood. Additionally, the factors that shape individual eating patterns remain uncertain, as they result from a complex mix of cultural, personal, physiological, and genetic influences.
Given this context, Olga Ramich, Heisenberg Professor at Charité – Universitätsmedizin Berlin and the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE), explored how the timing of daily food intake relates to glucose metabolism and insulin sensitivity. Ramich, who also works with the German Center for Diabetes Research (DZD), and her team aimed to identify the genetic and environmental factors that shape personal eating patterns.
The researchers drew on data from the NUtriGenomics Analysis in Twins (NUGAT) study, which involved 46 pairs of identical and fraternal twins who did not have diabetes. Participants recorded detailed food diaries over five consecutive days, noting both the timing and quantity of their meals. The team assessed each individual’s sleep-wake cycle (chronotype) and conducted several metabolic evaluations, including a glucose tolerance test. In addition, they calculated the circadian timing of food intake, meaning they analyzed when meals occurred in relation to each person’s internal biological clock rather than the clock time alone.
An important parameter that the scientists determined was the circadian caloric midpoint (CCM) of the test subjects. The CCM describes the time point in the day at which 50% of daily calories are consumed. A later CCM, therefore, means that someone eats mainly later in the day, in relation to the individual chronotype.
“People who ate their main calories earlier in the day had better insulin sensitivity,” explains Ramich, who heads the Department of Molecular Metabolism and Precision Nutrition at the DIfE. “On the other hand, subjects who consumed their main calories late in the day showed poorer insulin sensitivity, which is associated with a higher risk of type 2 diabetes.” In addition, they had a higher body mass index and a larger waist circumference.
To investigate the influence of genes on eating times, the researchers compared the eating behavior of identical twins (100 percent identical genes) with that of fraternal twins (approx. 50 percent identical genes). Using special mathematical models, they were able to estimate the extent to which the timing of eating can be attributed to genes, shared environment, or individual experiences.
The study shows that various parameters of the daily eating pattern are affected by our genes by up to 60 percent.
Shifting the main calorie intake to earlier circadian times might improve glucose metabolism and protect against type 2 diabetes and obesity. “However, as eating times are partly hereditary, some people may find it difficult to change their habits,” Ramich points out. “Further validation studies and clinical trials are needed to better understand the effectiveness of mealtime-based interventions.”
The timing of a person’s meals in relation to their internal biological rhythm is assessed by measuring the gap between when they eat and the midpoint of their sleep. This midpoint refers to the exact halfway point between falling asleep and waking up. It serves as an indicator of a person’s chronotype, meaning whether they tend to be more active in the morning or at night.
The NUGAT study, initiated and designed by Prof. Andreas F. H. Pfeiffer, was conducted from 2009 to 2010 at the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE). The identical and fraternal twin pairs were recruited either from a twin register (HealthTwiSt, Berlin, Germany) or via public advertisements. The 92 participants (46 pairs of twins) underwent two nutritional interventions, which were not relevant to the study results demonstrated.
The participants underwent detailed metabolic phenotyping, which included a physical examination, medical history, anthropometric measurements, and a glucose tolerance test. The individual chronotype was determined by means of a questionnaire. In addition, all 92 test subjects filled out handwritten food logs in which they noted the start and end of each meal as well as the amount and type of food consumed on five consecutive days. This included three working days and two days off to reflect the eating habits of the twin pairs.
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