There’s an old proverb saying that one must ‘Eat breakfast like a king, lunch like a prince, and dinner like a pauper,’ based on the assumption that consuming a high-calorie breakfast and reducing calories at dinner can optimize weight loss.
Calorie-loaded breakfast intake has long been recommended to improve weight loss. Several animal studies that suggested that the timing of meals can reduce weight gain also support this claim. However, the underlying mechanisms through which the timing of eating could promote weight loss in humans remain unclear.
A new study published in Cell Metabolism looked into how the time of day interacts with metabolism. The researchers found that regardless of whether a person eats their largest meal in the morning or late in the day does not affect the way their body digests calories. However, eating early in the morning has been reported to reduce appetite in the evening, which could help facilitate weight loss.
The study’s researchers recruited 30 healthy participants who were overweight or obese to have their diets controlled and their metabolisms measured over a period of time. They included 16 men and 14 women with an average age of 50.9.
The participants were randomly assigned to eat either a morning-loaded or an evening-loaded diet within four weeks. The diets were isocaloric, with a balance of 30% protein, 35% carbohydrate, and 35% fat.
After finishing 4 weeks on one diet, participants completed a series of tests and a washout diet before switching to the other diet for an additional 4 weeks.
The researchers recorded measures from the participants throughout the study, including:
The participants were able to lose an average of over 3 kilograms each during the 4-week periods.
Based on the data analysis from the participants, the researchers found that eating larger meals in the morning did not result in more weight loss or energy expenditure compared to those who ate larger meals in the evening.
However, the researchers also noted that participants on the morning meal diet reported having significantly lower hunger levels in the evening. Based on these findings, the researchers inferred that having a large breakfast could help facilitate weight loss by reducing appetite rather than influencing energy balance.
The study also mentioned several limitations which urge further research. One limitation of the study is that it was conducted under free-living conditions instead of in a lab. Certain metabolic measurements were also available only after breakfast and not after dinner.
The researchers also plan to expand their research into how the time of day affects metabolism by conducting studies similar to the one described here on subjects who do shift work. There’s a possibility that these individuals could have different metabolic responses due to the disruption of their circadian rhythms. It is also important to note that one diet does not fit all individuals, which is something that future researchers could ponder on.
Ruddick-Collins, L. C., Morgan, P. J., Fyfe, C. L., Filipe, J. A., Horgan, G. W., Westerterp, K. R., Johnston, J. D., & Johnstone, A. M. (2022). Timing of daily calorie loading affects appetite and hunger responses without changes in energy metabolism in healthy subjects with obesity. Cell Metabolism. https://doi.org/10.1016/j.cmet.2022.08.001