Scientists find: meal timing affects weight loss more than diet composition

Researchers at the University of Murcia in Spain have discovered that people can lose weight at different rates even on the exact same diet — and the key factor is meal timing. The observation was first made by nutrition specialist Marta Garaulet, who noticed a pattern among her patients: one of them ate lunch considerably later than the others, despite following an identical diet.

"That was the only difference," she told the BBC. Intrigued by the finding, Garaulet and her colleagues carried out a 20-week study involving more than 400 Spanish adults who all followed the same dietary programme. The results, published in the journal Nature, showed that those who ate lunch earlier lost weight faster and more effectively.

The body's internal clock

According to neuroscientist Frank Scheer, the different effects of eating the same food at different times of day come down to the body's internal biological clock. "Biologically speaking, we are different people in the morning than we are in the evening," he explained to the BBC.

When the body is already preparing for sleep and a person eats at that moment, a so-called circadian mismatch occurs. In a study published in 2022 in the journal Diabetes Care, 800 participants were given a glucose drink designed to mimic a typical evening meal in terms of carbohydrate content. Some drank it an hour before bedtime, while others drank it three hours before. The second group processed the glucose far more efficiently.

Scientists attribute this to the hormone melatonin, whose levels rise before sleep. "If you eat in the evening, when melatonin levels are elevated, your ability to regulate blood sugar is impaired," Scheer noted. Another study found that eating dinner late reduces the production of leptin, the hormone responsible for feelings of fullness. People who ate dinner later felt hungrier the next day and burned less energy than those who ate earlier.

Night owls and early birds

Everyone's internal clock works differently. According to an Italian study, people can be divided into three chronotypes: "early birds," who wake up early; "night owls," who naturally go to bed and wake up later; and an intermediate type.

Experts say "night owls" are more prone to unhealthy habits, since they often have to adapt their natural rhythm to fit work schedules rather than the other way around. This disrupts sleep quality and can trigger cravings for sugary or fatty foods to compensate.

What to eat, and when

In a recent review, experts from the Italian Society of Endocrinology and the Italian Society of Diabetology and Clinical Nutrition recommended including whole grains, legumes, fruit and other high-fibre, high-carbohydrate foods at breakfast and lunch.

In the evening, they suggest, meals should consist of vegetables, protein-rich foods and items that promote good sleep — nuts, seeds, poultry, fish, eggs and certain dairy products. All of these contain tryptophan, a compound known to improve sleep quality.

Source: denik.cz