Study examines why eating late at night increases obesity risk – Harvard Gazette

Obesity affects approximately 42% of the adult population in the United States and contributes to the onset of chronic diseases, including diabetes, cancer and other conditions.

While popular healthy eating mantras advise against midnight snacking, few studies have thoroughly investigated the simultaneous effects of late eating on the three main players in weight regulation and therefore obesity risk. : the regulation of caloric intake, the number of calories you burn and molecular changes in adipose tissue.

A new study by researchers at Harvard Medical School at Brigham and Women’s Hospital has found that the act of eating has a significant impact on our energy expenditure, appetite and molecular pathways in adipose tissue. Their results are published in Cell metabolism.

“We wanted to test the mechanisms that may explain why eating late increases the risk of obesity,” explained the lead author. Frank ScheerHMS Professor of Medicine and Director of the Medical Chronobiology Program for the Division of Sleep and Circadian Disorders at Brigham and Women’s.

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

“In this study, we asked whether the time we eat matters when everything else is consistent,” said first author Nina Vujović, a researcher in the Medical Chronobiology Program.

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

During the last two to three weeks before starting each of the lab protocols, participants maintained fixed sleeping and waking schedules, and during the last three days before entering the lab, they strictly followed identical diets and meal times at home.

In the lab, participants regularly documented their hunger and appetite, provided small blood samples frequently throughout the day, and had their body temperature and energy expenditure measured.

To measure how time to eat affected molecular pathways involved in adipogenesis, or how the body stores fat, researchers collected adipose tissue biopsies from a subset of participants during lab tests in the protocols. early and late feeding, to allow comparison of gene expression patterns between these two feeding conditions.

The results revealed that eating later had profound effects on hunger and the appetite-regulating hormones leptin and ghrelin, which influence our desire to eat. Specifically, levels of the hormone leptin, which signals satiety, decreased over 24 hours in the late feeding conditions compared to the early feeding conditions.

When participants ate later, they also burned calories at a slower rate and showed adipose tissue gene expression toward increased adipogenesis and decreased lipolysis, which promote fat growth.

In particular, these results reflect convergent physiological and molecular mechanisms underlying the correlation between eating late and increased risk of obesity.

Vujović explained that these findings are not only consistent with a large body of research suggesting that eating later may increase the likelihood of developing obesity, but they shed new light on how this might occur.

By using a randomized crossover design and tightly controlling behavioral and environmental factors such as physical activity, posture, sleep, and light exposure, researchers were able to detect changes in the various control systems involved in energy balance, a marker of how our bodies use the food we eat.

In future studies, Scheer’s team aims to recruit more women to increase the generalizability of their findings to a larger population. Although this study cohort only included five participants, the study was designed to control the menstrual phase, which reduces confounding but makes recruiting women more difficult.

Going forward, Scheer and Vujović also want to better understand the effects of the relationship between mealtime and bedtime on energy balance.

“This study shows the impact of late eating compared to early eating. Here, we isolated these effects by controlling for confounding variables such as calorie intake, physical activity, sleep, and exposure to light, but in real life many of these factors can themselves be influenced by mealtimes,” Scheer said.

“In larger-scale studies, where tight control of all of these factors is not possible, we need to at least consider how other behavioral and environmental variables alter these biological pathways underlying obesity risk,” did he declare.

This study was funded by R01DK099512, UL1TR001102 and UL1TR002541. FAJLS was supported by NIH grants R01DK099512, R01HL118601, R01DK102696 and R01DK105072 and R01HL140574. MJP and MJB were supported by DK020595. MG has been supported by the Spanish Government of Research, Development and Innovation (SAF2017-84135-R), including ERDF co-funding; the Autonomous Community of the Region of Murcia through the Seneca Foundation (20795/PI/18), and NIDDK R01DK099512. SLC was supported by the Alexander von Humboldt Foundation. JQ was supported by the American Diabetes Association (Award 1-17-PDF-103) and by the NIH (Grant K99HL148500 and R01DK102696).

Disclosures: During the execution of this project, Scheer received lecture fees from Bayer HealthCare, Sentara Healthcare, Philips, Vanda Pharmaceuticals and Pfizer Pharmaceuticals; received consulting fees from the University of Alabama at Birmingham; and served on the board of the Sleep Research Society. Scheer’s interests have been considered and managed by Brigham and Women’s Hospital and Partners HealthCare in accordance with their conflict of interest policies. None of these are related to work in progress. Vujović was paid for consultancy services provided to the Novartis Institutes for Biomedical Research, also unrelated to ongoing work.

About Hector Hedgepeth

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