Eating at night is a bad idea if you want to be at a healthy weight. A study now shows that the time we eat significantly influences our energy expenditure, appetite and molecular pathways in adipose tissue. Their results are published in “Cell Metabolism.”
Although popular healthy diet mantras discourage midnight snacking, few studies have comprehensively investigated the simultaneous effects of late eating on the three main players in body weight regulation and thus obesity risk: regulation of calorie intake, the number of calories burned, and molecular changes in fat tissue. Now this study provides the necessary scientific evidence.
“We wanted to check the mechanisms that may explain why eating late increases the risk of obesity,” explains the lead author, Frank A. J. L. Scheerdirector of the Medical Chronobiology Program in the Division of Sleep and Circadian Disorders at Brigham Women Hospital.
Although previous research had shown that eating late was associated with an increased risk of obesity, increased body fat, and less successful weight loss, the researchers wanted to understand why.
Does it matter what time we eat when everything else is held constant?
“We found that eating four hours later makes a significant difference to our hunger levels, the way we burn calories after eating, and the way we store fat,” says first author Nina Vujović,
Vujović, Scheer and their team studied 16 patients with a body mass index (BMI) in the range of overweight or obesity.
They each completed two lab protocols: one with a strictly scheduled early meal schedule, and the other with the exact same meals, each scheduled about four hours later in the day.
In the two to three weeks before starting each of the protocols, the participants maintained fixed sleep-wake schedules, and in the three days before, they strictly followed identical diets and meal times at home.
In the lab, the participants regularly documented their hunger and appetite, provided frequent small blood samples throughout the day, and had their body temperature and energy expenditure measured.
To measure how mealtime affected molecular pathways involved in adipogénesisthat is, how the body stores fat, the researchers obtained biopsies of adipose tissue from a subset of participants during laboratory tests in the early and late feeding protocols, to allow comparison of gene expression patterns/levels between these two feeding conditions.
The results revealed that eating later had profound effects on hunger and 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-eating condition compared to the early-eating conditions.
In addition, when the 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.
Eating 4 hours later makes a difference to our hunger levels, how we burn calories after eating and how we store fat
Vujović explains that these findings not only align with a large body of research suggesting that eating later may increase the likelihood of developing obesity, but also shed new light on how this might occur.
Using a randomized crossover study, and strictly controlling for behavioral and environmental factors such as physical activity, posture, sleep, and light exposure, the researchers were able to detect changes in the different control systems involved in energy balance, a indicator of how our body uses the food we eat.