Eating Before Bed Delays Fat Burning

For example the 16:8 fasting plan is becoming rather popular, in this plan you fast for 16 hours of the day, this time can include sleeping time, and after the 16 hours that leaves a window of 8 hours in which one must consume all of the caloric intake for the day. During the 16 hour fast one can only drink calorie free beverages such as water, or unsweetened teas and coffee. This anti-aging eating plan may help to support weight loss, improve blood sugar, brain function, and extend longevity. 

Research from Vanderbilt University Nashville suggests that it is not just the number of calories a person consumes that influences weight gain but also when a person consumes them. Findings relate to the biological clock/circadian rhythm which modulates hundreds of processes from sleeping to eating and body temperature to hormone levels. Having a disrupted circadian rhythm, such as one affecting those who are shift workers, has been associated with adverse health effects including obesity. 

“There are a lot of studies on both animals and humans that suggest it’s not only about how much you eat but rather when you eat,” explains Prof. Carl Johnson, senior author of the study and Cornelius Vanderbilt Professor of Biological Sciences.

To test the hypothesis the metabolism of 6 people was monitored when they consumed meals at different times during the day; participants were over the age of 50 and consumed three meals per day over two separate 56 hour sessions which both had the same overnight fasting period.

One session had the participants consume breakfast, lunch, and dinner; while the other session had the participants skip breakfast but have an extra meal as a late evening snack. The 8AM breakfast and 10PM late night snack both contained 700 calories and were nutritionally equivalent. In each session the amount of physical activity the participants engaged in was the same. 

Metabolism was monitored using Vanderbilt’s human metabolic chamber to provide continual measurements of metabolic rate as well as the breakdown of fats and carbohydrates. Despite having a consistent calorie intake and activity level it was found that the timing of food intake had a significant effect on how much fat the participants burned; when they had a late night snack the participants broke down less fat then when they consumed breakfast. 

According to the researchers the 10PM late night snack delayed the body’s ability to break down fat and caused it to break down carbohydrates instead; on average participants burned 15 grams more of lipids over 24 hours in the breakfast sessions than the late night snack sessions, which over time could lead to significant fat accumulation. 

“This confirms that the timing of meals during the daytime and nighttime cycle affects how ingested food is used versus stored, and that any food ingested prior to bedtime will delay the burning of fat during sleep,” explains first author and Vanderbilt postgraduate student Kevin Kelly.

Findings suggest that the circadian rhythm regulates fat burning which could have implications for eating habits and indicates that fasting from dinner to breakfast is better for weight loss than skipping breakfast.