Fasting at night or in the morning? Listen to your biological clock, says new research

In the first set of tests, the researchers presented one of the three daily meals as breakfast whereas in the second session, the team presented food equal in nutrition to the same subjects as a late-evening snack. 

They found that, while the two sessions did not differ in the amount of food eaten or the amount of physical activity of the participants, the daily timing of nutrient availability coupled with the body’s increased metabolism during sleep (thanks to the body’s circadian rhythms) flipped a switch on fat burning: In each instance, late-evening snacking delayed the body’s ability to target fat stores for energy and instead caused the body to target the readily accessible carbohydrates newly introduced into the body.

“The late-evening snack session resulted in less lipids oxidized than in the breakfast session,” said Kelly. “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.”

The study has important implications for eating habits, providing evidence contrary to a recent trend of skipping breakfast and suggesting instead a daily fast from supper to breakfast to help optimize weight management.

The project is funded by the National Institute of Neurological Disorders and Stroke and the National Institutes of Health.