Summary: Our bodies process food differently depending on the time of day, and consuming the bulk of daily calories later in the biological day has been linked to poorer metabolic health. A twin study found that those who concentrated most of their calories earlier in their personal day showed better insulin sensitivity and lower markers linked to type 2 diabetes and obesity.
The researchers also found that eating-time preferences are substantially influenced by genetics — in some measures up to 60% — which can make it more difficult for some people to shift their meal timing. These results indicate that personalized nutrition should account for both circadian rhythms and genetic predisposition when designing interventions.
Key Facts:
- Eating earlier in the individual biological day is associated with improved insulin sensitivity and lower diabetes risk.
- Genetic factors explain as much as 60% of individual differences in daily eating timing patterns.
- Effective personalized nutrition strategies should include circadian timing and hereditary influences on eating behavior.
Source: DZD
Our metabolic processes follow a daily rhythm and many are more active in the morning than in the evening.
While previous research has linked late eating to a higher risk of obesity and cardiovascular disease, less is known about how meal timing relative to an individual’s internal clock affects glucose metabolism and the degree to which those patterns are inherited. To explore these questions, Prof. Olga Ramich and colleagues at the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE) analyzed data from a twin cohort.
The research article was published in the journal eBioMedicine.
Metabolism follows the internal clock
The circadian system is a hierarchical, roughly 24-hour timing network in the body that coordinates behavior and metabolism through a central clock in the brain and peripheral clocks in organs such as the liver and pancreas. As a result, when we eat influences metabolic responses: glucose handling and hormone release after a meal show daily fluctuations. Meal timing itself acts as an important synchronizer for these internal clocks.
When meal schedules are misaligned with the natural light–dark cycle — for example, during night-shift work — this decoupling can disrupt circadian coordination and trigger adverse metabolic changes.
Does late eating increase disease risk?
Observational studies have associated late-night eating with a higher incidence of obesity and cardiovascular conditions. However, the mechanisms linking meal timing to glucose metabolism and diabetes risk are not fully clarified. Eating behaviour arises from cultural, personal, physiological and genetic contributors, and the interaction of these factors determines an individual’s timing of food intake.
Against this background, Olga Ramich — Heisenberg Professor at Charité – Universitätsmedizin Berlin and head of Molecular Metabolism and Precision Nutrition at DIfE — investigated how meal timing relative to a person’s internal clock correlates with glucose regulation and insulin sensitivity, and which genetic and environmental influences shape those eating patterns.
Twins reveal genetic influence
The team analyzed data from the NUGAT (NUtriGenomics Analysis in Twins) study, which included 46 twin pairs (both identical and fraternal) without diabetes. Participants kept detailed five-day food logs noting the timing, duration, and composition of each meal. Researchers also assessed sleep–wake timing (chronotype) and performed metabolic testing such as oral glucose tolerance tests.
By comparing meal times to each participant’s biological clock — rather than clock time alone — the investigators examined how eating relative to the individual circadian rhythm relates to metabolic outcomes.
Eating earlier supports healthier glucose metabolism
A key metric used in the study was the circadian caloric midpoint (CCM), defined as the time of day when a person has consumed 50% of their daily calories. A later CCM indicates that most calories are eaten later in the individual day, relative to that person’s chronotype.
Participants who ate the majority of their calories earlier in their circadian day demonstrated better insulin sensitivity. Conversely, those with a later CCM exhibited reduced insulin sensitivity — a known risk factor for type 2 diabetes — along with higher body mass index and larger waist circumference.
Genetic contribution to meal timing
To estimate heritability, the researchers compared correlations of eating-timing measures within monozygotic (identical) and dizygotic (fraternal) twin pairs and applied genetic structural equation models. The analyses showed that multiple aspects of daily eating patterns — including timing, calorie distribution and frequency — have moderate to high heritability. Some components of meal timing were influenced by genetic factors by up to about 60%.
Implications: Personalized nutrition must include circadian and genetic factors
Shifting the main portion of daily calories to earlier circadian times may improve glucose metabolism and help reduce the risk of type 2 diabetes and obesity. However, because meal timing tendencies are partly inherited, some individuals may face greater difficulty changing long-standing patterns. The authors recommend additional validation in larger cohorts and interventional trials to determine how effectively mealtime adjustments can be used to improve metabolic health.
Circadian timing of eating explained
Circadian timing of eating describes when meals occur in relation to an individual’s biological rhythm. In this study it was measured as the interval between the clock time of a meal and the midpoint of sleep — a chronotype marker that sits halfway between falling asleep and waking up. That midpoint reflects whether someone tends to be an early riser or a night owl and helps place eating patterns on each person’s internal clock.
NUtriGenomics Analysis in Twins (NUGAT) study details
The NUGAT study, designed by Prof. Andreas F. H. Pfeiffer, was conducted from 2009 to 2010 at the German Institute of Human Nutrition Potsdam-Rehbrücke. The 92 participants (46 twin pairs) underwent detailed metabolic phenotyping, which included medical history, anthropometric measurements, and glucose tolerance testing. Chronotype was assessed via questionnaire and all participants completed five-day handwritten food records documenting meal start and end times, quantities, and food types across three workdays and two days off to capture habitual patterns.
About this genetics and circadian rhythm research news
Author: Public relations DIfE
Source: DZD
Contact: Public relations DIfE – DZD
Image: The image is credited to Neuroscience News
Original Research: Open access. “Later eating timing in relation to an individual internal clock is associated with lower insulin sensitivity and affected by genetic factors” by Olga Ramich et al., published in eBioMedicine.
Abstract
Later eating timing in relation to an individual internal clock is associated with lower insulin sensitivity and affected by genetic factors
Background
Although the circadian clock’s role in metabolic regulation is well established, the specific contribution of meal timing to glucose homeostasis and diabetes risk remains underexplored. This study aimed to (i) link eating-timing patterns relative to the individual internal clock with glucose regulation and (ii) quantify genetic and environmental contributions to eating-timing parameters.
Methods
In 92 adult twins, glycaemic traits were measured with an oral glucose tolerance test. Eating-timing metrics (timing of meals, daily calorie distribution, and eating frequency) were extracted from five-day food records. The caloric midpoint was defined as the time when 50% of daily calories had been consumed. Circadian timing of eating was calculated as the interval between meal clock time and a corrected midpoint of sleep. Heritability estimates were obtained by comparing correlations in monozygotic and dizygotic twin pairs and by fitting genetic structural equation models.
Findings
Among the eating-timing variables, the circadian caloric midpoint (CCM) showed the strongest associations. A later CCM was significantly linked to poorer insulin sensitivity (lower ISI Stumvoll and higher HOMA-IR), higher fasting insulin, and, after adjustment for sex, age, daily energy intake, and sleep duration, to higher BMI and larger waist circumference. Most eating-timing components displayed moderate to high heritability and were closely related to individual sleep timing.
Interpretation
Eating later relative to one’s internal clock is associated with reduced insulin sensitivity. Moving the main calorie intake earlier in the circadian day could improve glucose metabolism, but genetic factors may limit how feasible or effective timing-based interventions are for some individuals. Further research in larger populations is warranted.
Funding
This work received support from the German Research Foundation, the European Association for the Study of Diabetes, and the German Federal Ministry of Education and Research. The German Center for Diabetes Research (DZD) is funded by the German Federal Ministry for Education and Research.