Eating late increases hunger, reduces calorie burning, and changes fat tissue

Obesity afflicts about 42 percent of U.
S.
adults and contributes to chronic diseases, including diabetes, cancer, and other diseases
.
While popular healthy diets advise against snacking at midnight, few studies have comprehensively investigated the simultaneous effects of eating late on three major factors in weight regulation and obesity risk: regulation of calorie intake, amount of calories burned, and molecular changes
in adipose tissue.
A new study by researchers from Brigham and Women's Hospital, a founding member of the Brigham Health System at Massachusetts General Hospital, found that the timing of our meals can significantly affect our energy expenditure, appetite, and molecular pathways
in adipose tissue.
Their findings were published in the
journal Cell Metabolism.

Senior author Frank A.
J.
L.
Scheer, Ph.
D.
, explains, "We wanted to test mechanisms
that might explain why eating late increases the risk of obesity.
" Frank A.
J.
L.
Scheer, Ph.
D.
, is director of
the Medical Chronobiology Program in Brigham's Sleep and Circadian Rhythm Disorders Unit.
"Previous studies by us and others have shown that eating late is associated
with an increased risk of obesity, increased body fat, and impaired weight loss success.
We want to know why
.
”

"In this study, we asked, 'Does it matter when we eat when everything else is consistent?'" Lead author Nina vujoviic, Ph.
D.
, is a researcher in
the Medical Chronobiology Program in Brigham's Sleep and Circadian Dysrhythmia Unit.
"We found that eating after 4 hours had a significant impact on
our hunger levels, the way we burn calories after meals, and the way we store fat.
"

vujoviic, Scheer and their team studied 16 patients
with a body mass index (BMI) in the range of being overweight or obese.
Each participant completed two protocols: one group was strictly scheduled for breakfast and the other group had exactly the same meal time, both scheduled about four hours later
that day.
For the last two to three weeks before starting each experiment, participants maintained a fixed sleep and wake schedule, and for the last three days before entering the lab, they strictly adhered to the same diet and diet schedule
.
In the lab, participants regularly recorded their hunger and appetite, frequently provided small samples of blood throughout the day, and measured their body temperature and energy expenditure
.
To measure how eating time affects molecular pathways involved in fat formation, or how the body stores fat, the researchers collected a subset of participants' adipose tissue biopsies in lab tests of early and late feeding protocols in order to compare gene expression patterns/levels
under these two feeding conditions.

The results showed that eating late had a profound effect on hunger and appetite-regulating hormones leptin and ghrelin, two hormones that affect our desire
to eat.
Specifically, leptin hormone levels that showed satiety decreased in the 24 hours of late feeding compared to early eating
.
When participants ate late, they also burned calories more slowly and showed that adipose tissue gene expression increased fat production and decreased lipolysis, which promoted fat growth
.
Notably, these findings convey the physiological and molecular mechanisms of convergence, hidden in the correlation
between late eating and increased obesity risk.

Vukoviic explained that the findings are not only consistent with a large body of research that says eating late may increase a person's likelihood of being obese, but they provide new clues
as to why this may occur.
By using randomized crossover studies and tightly controlling behavioral and environmental factors such as physical activity, posture, sleep, and light, the researchers were able to detect changes in different control systems involving energy balance, which is a marker
of how our bodies use the food we consume.

In future studies, the research team plans to recruit more women to increase the generalizability
of their findings to the wider population.
Although there were only 5 female participants in the study cohort, the study was designed to control menstrual periods, reducing confusion but making it more difficult
to recruit women.
Looking ahead, Scheer and Vujovik are also interested in
better understanding the impact of the relationship between meal time and bedtime on energy balance.

"This study shows the effects of
eating late and eating early.
Here, we isolate these effects by controlling for confounding variables such as caloric intake, physical activity, sleep, and light, but in real life, many of these factors may themselves be affected by mealtimes, and in larger studies, strictly controlling for all of these factors is not feasible, and we must at least consider how other behavioral and environmental variables alter the biological pathways
of these potential obesity risks.
”