An article published in Cell Metabolism by Vujovic and colleagues on October 4, 2022 described their research comparing weight gain when eating an early breakfast compared to eating a late one. Their article was referenced in the AMA Morning Rounds on October 5, 2022.
The research identified several differences between test subjects who ate breakfast at different times. Eating early was defined as eating at about 9 am; eating late was eating breakfast 250 minutes later. The amount of nutrients were identical, and the amount of sleep, exercise and light exposure were the same.
Eating breakfast around noon resulted in several adverse outcomes for people wanting to limit weight gain. It resulted in more daytime hunger, less 24-hour leptin (hormone that decreases hunger), less energy used, lower core body temperature, and altered fat tissue gene expression that leads to increased fat storage.
The researchers stated, “combined, these changes upon late eating may increase obesity risk in humans.” They attributed these differences to effects related to the “circadian timing system.” This system is involved with a variety of biological differences affected by our 24-hour internal clock.
The bottom line is that eating breakfast closer to noontime likely causes more weight gain than eating the same food around 8-9 am.
Peter M. Hartmann, MD
Family Medicine and Psychiatry
