Scientists have studied the relationship of late sleep and eating with metabolism in obesity

Adults with obesity and late chronotype were more likely to have several signs of metabolic syndrome at once than participants with early chronotype. The highest rates were observed in those who combined a late sleep schedule with a meal after eight in the evening, although for this combination we are talking about a statistical trend. About how scientists linked the daily routine with the state of the intestinal barrier and what the microbiome analysis showed is in the Izvestia article.

Who did the researchers classify as "owls"

A team from the University of Texas Health Sciences Center at Houston and her colleagues analyzed data from 87 obese adults. The average age of the participants was 42.5 years, and the average body mass index was 37.5 kg/m. The data was taken from a clinical trial that examined drugs that affect the intestinal microbiome. For the new analysis, the researchers compared the initial information about the participants' health and their usual routine.

The chronotype was determined by a questionnaire about sleep on working and free days. For the calculation, we took the average amount of sleep on free days and took into account that people can sleep longer, making up for lack of sleep in a week. The chronotype was considered to be late, in which this point occurred after three o'clock in the morning. According to this criterion, 59 out of 87 people were classified as "owls".

The meal time was determined by a separate questionnaire, which included snacks. The late group included people who ate after 20:00. Eight p.m. was the boundary chosen by the researchers for comparison. The participants reported on their usual routine, and they were not assigned a meal time.

What was found in people with a late chronotype

Metabolic syndrome combines disorders that increase the risk of type 2 diabetes, cardiovascular disease, and stroke. Criteria include increased waist circumference, high blood pressure, high levels of fasting glucose and triglycerides, as well as low levels of high-density lipoprotein cholesterol. A diagnosis usually requires at least three such signs, according to the US National Heart, Lung, and Blood Institute.

Autumn fatigue: how to stop wanting to sleep and regain energy

The group with increased metabolic load included participants with two or more symptoms. These were 42 out of 59 among "owls" (71.2%) and 13 out of 28 among people with an early chronotype (46.4%). Based on this result, it is possible to judge the number of people with several risk factors in each group. The proportion of participants who already had grounds for a clinical diagnosis would be considered at a different threshold.

When comparing sleep and nutrition combinations, the difference was also noticeable. Two or more signs were found in 16 of the 22 "owls" who ate after 20:00, and in six of the 14 participants with an early chronotype who completed their meal by eight in the evening. The general trend for four combinations of chronotype and meal time has not reached the generally accepted threshold of statistical significance. A larger sample is needed to reliably assess the combination of factors.

Why did scientists study the intestinal barrier?

The central biological clock is located in the brain, and individual organs have their own circadian rhythms. The rhythm of the intestine, in particular, is influenced by the time of meals. The authors wanted to find out whether the combination of late sleep and eating is accompanied by changes in the functioning of the intestinal barrier and the composition of the microbiome.

Intestinal cells form a barrier that allows the absorption of nutrients and limits the penetration of intestinal contents into the blood. To assess its permeability, the researchers used a test with several types of sugars. By the amount of these substances in the urine, it was possible to indirectly judge the permeability of different parts of the intestine. The participants with late meals had higher individual scores on this test.

The authors also compared the results with laboratory indicators of metabolism and inflammation. To do this, they compiled a composite index of 15 indicators selected based on the data from this group. The association of a combination of a late chronotype and a late meal with a higher index value was stronger among participants with increased intestinal permeability. The authors consider this index as a research tool. For its application in other groups, a separate check would be needed.

In the stool samples of participants with a late chronotype, a lower representation of a number of bacterial groups was found, which in other studies were associated with the formation of short-chain fatty acids. Such substances are produced during the processing of food components by microbes, and some of them are involved in maintaining the intestinal barrier. In this work, the acids themselves were not measured. Scientists assessed the composition of the microbiome and judged by it what its potential could be.

What the experiment with the microbiome showed

In the initial trial, participants received prebiotics, probiotics, a combination of both, or a placebo for three weeks. In the new analysis, the researchers looked at the differences between people who had decreased intestinal permeability after the test in response to the test load. Some of them have more bacteria associated with the formation of short-chain fatty acids. This result helps to formulate a hypothesis about the role of the microbiome, but by itself it does not show which remedy could reduce the metabolic risk.

The analysis of sleep and meal times was observational, although the data was taken from a randomized trial. The groups were randomly assigned according to the means for the microbiome, and the sleep and nutrition schedule remained the same. Therefore, it is impossible to tell from work whether the state of the intestinal barrier will change if a person starts eating earlier. The authors suggest testing this in studies where it will be possible to change the time of meals and monitor the condition of the same participants.