Eating Late Increases Hunger, Decreases Calories Burned, And Changes Fat Tissue

Conventional nutrition recommendations advise against late night snacking but mostly because of the types of foods people usually reach for – highly processed, high fat, high carb snack foods. However, very few studies have comprehensively investigated the simultaneous effects of late eating and the factors that control body weight:  regulation of calorie intake, how many calories you burn and the molecular changes in fat tissue – until now.

A new study published in Cell Metabolism found that when we eat significantly impacts our energy expenditure, appetite and molecular pathways in adipose (fat) tissue.  The study aimed to answer “does the time that we eat matter when everything else is kept consistent?”

The research team studied 16 individuals with a BMI in the overweight or obese range. Each participant completed 2 different protocol: one with a strictly scheduled early meal schedule, and the other with the exact same meals, each scheduled about 4 hours later in the day.  Participants maintained fixed sleep and wake schedules.  During the experiment, participants documented their hunger and appetite, provided frequent blood samples throughout the day and had their body temperature and energy expenditure measured. To measure how eating time affected molecular pathways involved in how the body stores fat, investigators collected biopsies of adipose tissue in both the early and late eating protocols to enable comparison of gene expression patterns/levels between these two eating conditions.

Results revealed that eating later in the day had profound effects on hunger and appetite-regulating hormones leptin and ghrelin. Levels of Leptin specifically, the hormone which signals satiety and tells us to stop eating, was decreased in the 24 hours following a day of late eating.  When participants ate later, they also burned calories at a slower rate and exhibited gene expression that promoted fat growth.

This study demonstrates a relationship between eating later and increased obesity risk – even if calories, sleep, activity and other confounding factors are controlled for. While other studies have demonstrated a similar correlation, this study sheds new light on how this might occur.

While this is exciting new research that can undoubtedly help nutrition professionals better guide clients to manage obesity risk, there are some limitations to the study.  The sample size was only 16 participants which is quite small. The study cohort only included 5 female participants. Controlling for menstrual phase made recruiting women more difficult. Future research that includes a wider diversity of participants will make the findings in this study more applicable to the general population.