Timing of meals impacts glucose tolerance and health

Although people have always said that having a light and early dinner is better, a study by the Universitat Oberta de Catalunya (UOC) and Columbia University has provided the scientific grounds for this argument. According to a study published in open access format by the Nature group journal Nutrition & Diabetes, consuming more than 45% of our daily calorie intake after 5 p.m. is associated with an increase in glucose levels, with the harmful consequences that this has for health, regardless of the individual's weight and body fat.

The study was carried out at Columbia University's Irving Medical Center in New York, and was led by Dr. Diana Díaz Rizzolo, postdoctoral researcher and member of the Faculty of Health Sciences at the UOC.

Maintaining high levels of glucose over long periods of time can have implications including a higher risk of progressing to type 2 diabetes, an increase in cardiovascular risk due to the damage that high glucose levels do to blood vessels, and increased chronic inflammation, which aggravates cardiovascular and metabolic damage."

Dr. Diana Díaz Rizzolo, postdoctoral researcher and member of the Faculty of Health Sciences, UOC

Experts had previously believed that the main consequence of eating dinner late in the day was weight gain. This was associated with the fact that people tend to make poorer dietary choices at night, such as consuming more ultra-processed foods, since the hormones that regulate hunger and satiety are altered when people do not eat during daylight hours.

The importance of the study lies in the fact that it shows that the time of day when meals are eaten can in itself have a negative impact on glucose metabolism, regardless of the amount of calories consumed throughout the day and the individual's weight and body fat.

"The time of day when meals are eaten can in itself have a negative impact on glucose metabolism"

Late eaters versus early eaters

The study included 26 participants between the ages of 50 and 70 who were overweight or obese, and had prediabetes or type 2 diabetes. The participants' glucose tolerance levels were compared, and they were divided into two groups: early eaters, who consumed most of their daily calories before the evening, and late eaters, who consumed 45% or more of their calories after 5 p.m. The two groups consumed the same amount of calories and the same foods during the day, but did so at different times. The participants used a mobile app to record their meals in real time.

The main finding of the study is that the late eaters had a poorer tolerance of glucose, regardless of their weight or the composition of their diet. It also found that they tended to eat larger amounts of carbohydrates and fats during the evening.

Díaz Rizzolo, who is an expert on issues related to obesity, diabetes and ageing, explained that "the body's ability to metabolize glucose is limited at night, because the secretion of insulin is reduced, and our cells' sensitivity to this hormone declines due to the circadian rhythm, which is determined by a central clock in our brain that is coordinated with the hours of daylight and night."

The importance of eating at the right time

The study therefore contains an important finding in terms of its implications for health and the time of day that people eat their meals. "Until now, personal decisions in nutrition have been based on two main questions: how much we eat, and what foods to choose. With this study, a new factor in cardiometabolic health is beginning to become increasingly important: when we eat," said Díaz Rizzolo.

In view of the results of the study, and considering them with due caution, since further research to gain a greater understanding of the subject will be required, the researcher advises that food should mainly be eaten during daylight hours, and that "the highest levels of calorie intake during the day should be at breakfast and lunch, instead of at teatime and dinner". Díaz Rizzolo also recommends avoiding eating ultra-processed products, fast food and foods rich in carbohydrates, especially at night.

This UOC study supports Sustainable Development Goal (SDG) 3, Good Health and Well-being.