The dangers of a late dinner have been scientifically proven: scientists have explained how it is harmful

Late-night raids on the fridge have long been a sad joke among people who want to lose weight but can't. They blame their desire to eat under the cover of night for the failure of all their efforts. And now scientists have explained how this habit prevents weight loss.

According to SciTechDaily, researchers at Brigham and Women's Hospital (part of Harvard Medical School) have found experimental evidence that late-night eating reduces energy expenditure, increases hunger, and changes adipose tissue at the molecular level in ways that may increase the risk of obesity. They published their findings in the scientific journal Cell Metabolism.

"We wanted to test the mechanisms that might explain why eating late increases the risk of obesity," explained senior author Dr. Frank Scheer. The scientist is the director of the Medical Chronobiology Program in the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital, so he is well versed in the changes that occur in the human body during the day. His team decided to find out why eating late increases the risk of obesity and body fat and reduces the chances of successful weight loss.

His colleague Nina Vujovic formulated the question that the scientists asked as follows: does the time at which we eat matter if everything else remains the same? And the team of researchers found that shifting the time of eating four hours ahead significantly affects the level of hunger, the way we burn calories after eating, and how our bodies store fat.

The study involved 16 people with body mass indexes ranging from overweight to obese. Each participant completed two laboratory protocols: one with a rigidly planned early meal schedule, and the other with the same meals, but shifted four hours later.

Two to three weeks before starting each protocol, the participants began to follow a sleep schedule determined by the researchers. In addition, they switched to the diet they would be testing three days before starting the laboratory tests. Thus, they did not have a drastic change in lifestyle.

During the study, the researchers monitored the participants' body temperature and energy consumption, and often collected small blood samples throughout the day. The subjects also recorded their hunger and appetite levels.

In addition, the researchers took biopsies of adipose tissue from some participants to measure how meal times affect the molecular mechanisms of adipogenesis (the formation of adipocytes, or fat cells), and thus how the body stores fat. The researchers wanted to compare gene expression patterns during two different nutrition protocols - early and late.

The results showed that a later meal greatly increases hunger and alters the function of the hormones leptin and ghrelin, which are responsible for appetite and the desire to eat. In particular, ghrelin, which signals satiety to the brain, had reduced levels within 24 hours of a late meal compared to levels after an early dinner.

When the participants ate later, they also burned calories more slowly and showed an increase in adipose tissue gene expression and a decrease in lipolysis (fat breakdown), meaning that the amount of body fat gradually increased.

Vujovic explains that these results are not only consistent with a large number of studies that have pointed to the dangers of eating late, but also shed new light on how exactly this happens. By using a randomized crossover study and carefully controlling for behavioral and environmental factors such as physical activity, posture, sleep, and light exposure, the researchers were able to detect changes in various systems that control the body's energy balance, markers of how our bodies use the food we eat.

The drawback of the study, as pointed out by the researchers themselves, was the involvement of a small number of women. There were only five of them in the group of subjects. And in their case, more measurements were taken. In particular, scientists monitored their menstrual cycle. That is why it was more difficult to recruit enough female participants. In the future, Scheer and Vujovic plan to study the reaction of the female body to a late meal more thoroughly. In addition, the scientists want to deepen their understanding of the impact of the relationship between meal times and sleep times on energy balance.