Thinking of having a midnight snack? Think again. That midnight snack you crave can contribute to an increased risk of obesity, and an increase in body fat, keeping one from successfully losing weight. Nearly half of the U.S. adult population is considered obese. Obesity can result in chronic diseases such as cancer, diabetes, and other health-related problems.
But what is it about a snack after midnight or late-night eating, for that matter, that contributes to such unhealthy side effects? While plenty of diet trends have advised against late-night eating, few have investigated why. Wanting to understand why, investigators from the Brigham and Women's Hospital took it upon themselves to test the mechanisms that could explain why late-night eating is associated with an increased risk for obesity.
Assessing 16 patients with a BMI (Body Mass Index) in the range of overweight or obese the team of investigators sought to comprehensively investigate the simultaneous effects of late-night snacking on the three main components of obesity and body weight regulation: calorie intake, the number of calories burned, and molecular changes in fatty tissue.
Each patient completed two laboratory protocols: one was a very strictly scheduled early meal schedule, while the other was the same meals scheduled roughly 4 hours later in the day. The patients kept a fixed sleep and wake schedule during the last two to three weeks before beginning each in-laboratory protocol. And for the final three days, the patients followed identical diets and scheduled meals at home before entering the lab.
Once in the lab, the patients documented their hunger and appetite, gave frequent small samples of blood throughout the day, and had their energy expenditure and body temperatures measured. To measure how the time of eating affected the molecular pathways involved in how the body stores fat, or adipogenesis, the investigators took biopsies of adipose from some of the patients throughout the laboratory testing, comparing the gene expression patterns/levels between both the early and late eating protocols.
The results showed that eating later significantly affected hunger hormones ghrelin and leptin, appetite-regulating hormones that influence our desire to eat. Levels of leptin (a hormone that signals satiety) were lower for the 24 hours in the later eating conditions as opposed to the earlier eating conditions. And when the patients ate later, they burned calories at a slower rate, exhibiting an increase in adipogenesis and a decrease in lipolysis, thus contributing to fat growth.
These recent findings are consistent with previous research on the correlation between late-night eating and increased risk of obesity while also providing the why of how when we eat can significantly impact appetite, how calories are burned, and how our bodies store fat.
While this study illustrates how late eating versus early eating affects hunger, energy expenditure, and the way our bodies store fat, future studies will aim to better understand how the relationship between mealtime and bedtime affects energy balance while taking into consideration how other behavioral and environmental variables also influence these biological pathways underlying obesity risk.