Skipping breakfast is not a good diet idea. Studies have shown that an energy deficit in the morning can trigger migraine attacks. Eating late can also lead to hunger and weight gain. A new study in Cell Metabolism (2022; DOI: 10.1016/j.cmet.2022.09.007) shows that it can not only lead to increased hunger pangs throughout the day, but also reduce energy expenditure. Ultimately, fat stores fill up, resulting in weight gain. A crossover study conducted by sleep researchers at Harvard Medical School in Boston now provides the explanation for the failure of the breakfast-skipping diet.

While common mantras for healthy eating advise against nighttime snacking, few studies have comprehensively investigated the simultaneous effects of late eating on the three main players in weight regulation and thus the risk of obesity:

  • the regulation of calorie intake,
  • the number of calories burned and
  • the molecular changes in adipose tissue.

A new study by researchers at Harvard Medical School has revealed that the timing of meals has a significant impact on energy consumption, appetite, and molecular processes in adipose tissue.

“We wanted to investigate the mechanisms that could explain why eating late increases the risk of obesity,” explained lead author Frank Scheer, Professor of Medicine and Director of the Medical Chronobiology Program in the Department of Sleep and Circadian Disorders at Brigham and Women's Hospital.

“Previous research by us and others had shown that eating late is associated with an increased risk of obesity, increased body fat, and poorer weight loss success. We wanted to understand why,” he said.

“In this study, we asked whether the time we eat makes a difference when everything else remains the same,” said first author Nina Vujović, a researcher in the Medical Chronobiology Program.

“And we found that eating four hours later makes a significant difference in terms of how we feel hungry, how we burn calories after eating, and how we store fat.”

Vujović, Scheer, and their team studied 16 patients with a body mass index in the overweight or obese range. Each participant completed two laboratory protocols: one with a strictly planned early meal and the other with the same meals consumed approximately four hours later in the day.

In the last two to three weeks before the start of each laboratory protocol, the participants maintained fixed sleep and wake times, and in the last three days before entering the laboratory, they strictly adhered to identical diets and meal plans at home.

In the laboratory, participants regularly documented their hunger and appetite, frequently took small blood samples throughout the day, and had their body temperature and energy consumption measured.

To measure how mealtime affects the molecular signaling pathways involved in adipogenesis, i.e., how the body stores fat, researchers took adipose tissue biopsies from a subset of participants during laboratory tests, both in the early and late meal protocols, to allow a comparison of gene expression patterns/values ​​between these two eating conditions.

The results showed that eating later had profound effects on hunger and the appetite-regulating hormones leptin and ghrelin, which influence our desire to eat. In particular, the level of the hormone leptin, which signals satiety, was lower over a 24-hour period under conditions of late eating than under conditions of early eating.

When participants ate later, they also burned fewer calories and showed gene expression in adipose tissue that suggests increased adipogenesis and decreased lipolysis, which promote fat growth.

These results suggest converging physiological and molecular mechanisms underlying the association between late eating and increased obesity risk.

Vujović explained that these results not only align with a wealth of research suggesting that eating later in life increases the likelihood of developing obesity, but also shed new light on how this might happen.

The effects on energy metabolism are significant. Both groups consumed the same number of calories. In the late eaters, these calories were stored more extensively in fat tissue.

An early and good breakfast counteracts hunger during the day, reduces the risk of being overweight, and can also help reduce the risk of migraines, as other studies have shown.

Source:

Vujović N, Piron MJ, Qian J, Chellappa SL, Nedeltcheva A, Barr D, Heng SW, Kerlin K, Srivastav S, Wang W, Shoji B, Garaulet M, Brady MJ, Scheer FAJL. Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity. Cell Metab. 2022 Oct 4;34(10):1486-1498.e7. doi: 10.1016/j.cmet.2022.09.007. PMID: 36198293.
https://doi.org/10.1016/j.cmet.2022.09.007