The way glucose is regulated at night plays a key role in fasting glucose levels the next morning, when blood sugar is expected to be at its lowest. This indicator is particularly important in people with dysglycemia, which is characterized by abnormal glucose levels. However, little research has been done in this area. Now, a study involving the Universitat Oberta de Catalunya (UOC) has shown that the last meal of the day plays a crucial part in regulating glucose levels the following morning, a factor that can be especially critical for people with prediabetes and may prove decisive in preventing the onset of this chronic disease.

According to the World Atlas of Diabetes, Spain has one of the highest rates of diabetes in Europe, ranking fifth overall. It affects 14% of the population – over five million people – and costs the health system more than €14 million each year.
The study, Biological vs. Chronological Overnight Fasting: Influence of Last Evening Meal on Morning Glucose in Dysglycemia, published as open access in Nutrients, analyses the role of fasting glucose levels after the last meal of the day, showing that carbohydrate consumption and the individual's sensitivity to insulin both have an impact. This discovery may have implications for the dietary recommendations given to individuals with prediabetes to prevent them from developing the disease. "Recommendations regarding the intake of carbohydrates and calories in the last evening meal could be tailored in line with the patient's insulin sensitivity. And blood glucose levels after this meal (postprandial glycemic response) could be monitored so that dietary or pharmacological treatments can be adjusted. This would allow for more personalized and adaptive blood glucose management," said Diana Díaz-Rizzolo, lecturer in the UOC's Faculty of Health Sciences and a member of the Nutrition, Food, Health and Sustainability (NUTRALiSS) research group, affiliated to the Digital Health, Health and Well-being Research Unit. Díaz-Rizzolo is also a postdoctoral researcher at Columbia University, which took part in the study.


Meal times and chronotypes also matter

The study, conducted by the UOC in collaboration with research institutions in the US, analysed 33 men and women aged 50 to 75 who were overweight or obese and had prediabetes, meaning their blood glucose levels were higher than normal but not yet in the diabetic range. After a day with a controlled diet and meal times, their glucose levels were measured the next morning following a 10-hour overnight fast. Patients wore a continuous glucose monitor to constantly control their blood sugar levels.

The results of the research show that dietary recommendations should consider not only the amount of carbohydrates patients can consume, as is usually the case, but also the timing of the last evening meal. The later the meal, the harder it becomes to regulate glucose, as the researchers had previously shown, while its nutritional content remains crucial for controlling overnight glucose levels. The researchers also found that an individual's insulin sensitivity influences glucose regulation.

Díaz-Rizzolo believes that our chronotype – whether we are morning or evening people – can also play an important role: "Our internal biological clock could play a key role in overnight glucose metabolism and fasting glucose levels. This information could be vital for making more personalized recommendations, taking into account not only insulin sensitivity, but also each individual's circadian profile (morning versus evening people). Understanding how chronotype and glycemic response interact could make diabetes prevention and management strategies more precise," she explained.

Díaz-Rizzolo argues that dietary recommendations for patients with prediabetes or insulin resistance should be based on:
- Controlling the composition and glycemic load of the last meal of the day, avoiding an excessive amount of carbohydrates.
- Adjusting the amount of carbohydrates according to the individual's insulin sensitivity, as patients with lower sensitivity may have a worse glycemic response.
- Considering the timing of meals to avoid nighttime glycemic spikes that can interfere with metabolism and fasting glucose.


New technologies: a turning point in diabetes management

Continuous glucose monitors, mobile apps to track our diets and artificial intelligence platforms that allow more detailed and real-time monitoring of glucose are changing the way patients manage their diabetes. "These tools," said Díaz-Rizzolo, "can greatly improve patients' quality of life and metabolic control. They help to detect glycemic imbalances early, allowing diet, medication and physical activity to be adjusted according to objective data. And they enable patients to participate actively in their treatment on an informed basis."

Díaz-Rizzolo and colleagues from the earlier study have recently presented a new methodology that uses artificial intelligence algorithms to automatically and reliably measure the actual time spent fasting, what's known as the biological overnight fast (BOF). This innovative method, presented at the American Diabetes Association Congress in Chicago, shows how overnight fasting impacts blood sugar levels in patients with prediabetes and type 2 diabetes.
"Combining the use of continuous glucose monitors with these algorithms can help people know how the time or type of meal they eat in the evening determines their glucose levels, together with the BOF, which could be a marker of metabolic health," Díaz-Rizzolo said. These tools will also make it possible to identify metabolic subtypes and postprandial response patterns, something conventional methods cannot achieve, thereby enabling more personalized treatment based on a deeper understanding of each patient's metabolism.

"The world of artificial intelligence in medicine is opening doors that we could never have imagined. In metabolic diseases, it can help us make early predictions of the risk of developing diabetes and complications. It can also be useful for jointly analysing genetic and epigenetic risk factors, metabolomics and the composition of the intestinal microbiota, which will help us to tailor treatments even further," she explained.


This study is aligned with the UOC's research mission on digital health and planetary well-being, and contributes to UN Sustainable Development Goal 3, good health and well-being.


Research at the UOC

Specializing in the digital realm, the UOC's research contributes to the construction of future society and the transformations required to tackle global challenges.
Over 500 researchers and more than 50 research groups make up five research units, each with a mission: Culture for a critical society, Lifelong education, Digital health and planetary well-being, Ethical and human-centred technology and Digital transition and sustainability.

The university's Hubbik platform fosters the development of UOC community knowledge transfer and entrepreneurship initiatives.

The goals of the United Nations 2030 Agenda for Sustainable Development and open knowledge are strategic pillars that underpin the UOC's teaching, research and knowledge transfer activities. For more information, visit research.uoc.edu.

Research at the UOC

Specializing in the digital realm, the UOC's research contributes to the construction of future society and the transformations required to tackle global challenges.

Over 500 researchers and more than 50 research groups make up five research units, each with a mission: Culture for a critical society, Lifelong education, Digital health and planetary well-being, Ethical and human-centred technology and Digital transition and sustainability.

The university's Hubbik platform fosters the development of UOC community knowledge transfer and entrepreneurship initiatives.

The goals of the United Nations 2030 Agenda for Sustainable Development and open knowledge are strategic pillars that underpin the UOC's teaching, research and knowledge transfer activities. For more information, visit research.uoc.edu.