Late eating is associated with impaired glucose metabolism
Our bodies process food differently depending on the time of day and many metabolic processes are more active in the morning than in the evening. Although studies show that late eating is associated with an increased risk of obesity and cardiovascular disease, little is known about how the timing of eating affects glucose metabolism and how much of this is genetically determined. Prof. Olga Ramich from the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE) and her team recently investigated this in a twin cohort. The article has been published in the journal eBioMedicine.
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Metabolism follows the internal clock
The circadian system is a hierarchically structured 24-hour time control system in the body that regulates behavior and metabolism via a central clock in the brain and peripheral clocks in organs such as the liver or pancreas. As a result, our body processes the same food differently depending on the time of day, which leads to diurnal fluctuations in glucose metabolism and the release of hormones after a meal. Food intake itself acts as an important timer that synchronizes our internal clocks. Decoupling eating time from the natural light-dark rhythm, such as when working at night, can lead to an internal clock disorder and negative metabolic changes.
Does eating late make you ill?
Previous studies have shown that eating late or at night is associated with an increased risk of obesity and cardiovascular disease. However, little is known about how exactly the timing of food intake interacts with the individual circadian rhythm to influence glucose metabolism and the risk of diabetes. It is also unclear which mechanisms determine individual eating behavior, as cultural, personal, physiological and genetic influences interact.
Against this background, Olga Ramich, Heisenberg Professor at Charité - Universitätsmedizin Berlin and DIfE, investigated how the timing of food intake during the day is related to glucose metabolism and insulin sensitivity. Ramich, who also conducts research at the German Center for Diabetes Research (DZD), and her team also wanted to find out what influence genetic and environmental parameters have on individual eating habits.
Twins provide information
To do this, they used data from the NUtriGenomics Analysis in Twins (NUGAT) study, in which 46 identical and fraternal twin pairs without diabetes took part. The test subjects kept a food diary of their eating times and quantities for five days. The scientists determined the individual sleep-wake rhythm (chronotype) of the participants and carried out various metabolic tests, such as a blood glucose load test. They also determined the circadian timing of eating, i.e. when someone eats during the day - in relation to the individual biological circadian rhythm and not to the time of day.
Eating earlier promotes a healthy metabolism
One important parameter that the scientists determined was the test subjects' circadian caloric midpoint (CCM). This describes the point in the day at which half of the daily calorie intake is calculated. A later CCM therefore means that someone eats mainly later in the day - in relation to the individual chronotype.
"People who consumed their main calories earlier in the day had better insulin sensitivity," explains Ramich, who heads the Department of Molecular Metabolism and Precision Nutrition at 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.
Genes influence when we eat
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 is attributable to genes, shared environment or individual experiences.
The study shows that various parameters of the daily eating time pattern are influenced by up to 60 percent genetics.
Conclusion: Personalized nutrition needs new approaches
Shifting the main calorie intake to earlier circadian times could 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 interventions based on mealtime."
Background information
Circadian timing of eating
When someone eats during the day in relation to their individual biological circadian rhythm is measured as the distance between mealtime and the midpoint of sleep. The midpoint of sleep describes the time that lies exactly in the middle between falling asleep and waking up. It is considered a measure of chronotype - i.e. whether someone is an early riser or a night owl.
NUtriGenomics Analysis in Twins (NUGAT) study
The NUGAT study, initiated and designed by Prof. Andreas F. H. Pfeiffer, was conducted at the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE) from 2009 to 2010. The monozygotic and dizygotic twin pairs were recruited either from a twin register (HealthTwiSt, Berlin, Germany) or via public advertisements. The 92 participants (46 twin pairs) underwent two nutritional interventions, which were not relevant to the study results shown here.
The participants underwent a 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. These included three working days and two days off to reflect the eating habits of the twin pairs.
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
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