There are a lot of myths surrounding the timing of eating and how it might influence either body weight or health. There’s the old saying in dieting that one must “breakfast like a king, lunch like a prince, and dine like a pauper,” based on the belief that consuming the bulk of daily calories in the morning optimizes weight loss by burning calories more efficiently and quickly.
Since timing and distribution of food intake is a modifiable lifestyle behavior, there is interest in understanding if timing of eating and distribution of food intake influences the success of weight-loss diets in humans.
Is this saying a fact?
Professor Alexandra Johnstone, a researcher in the field of appetite control at the Rowett Institute, University of Aberdeen, Scotland and her team, recruited healthy subjects who were overweight or obese to have their diets controlled and their metabolisms measured over a period of time; 16 men and 14 women completed the study.
Each participant was randomly assigned to eat either a morning-loaded or an evening-loaded diet for four weeks. The diets were isocaloric, with a balance of 30% protein, 35% carbohydrate, and 35% fat.
After a washout period of one week in which calories were balanced throughout the day, each participant crossed over to the opposite diet for four weeks. In that way, each participant acted as their own study control.
Throughout the study, the subjects’ total daily energy expenditures were measured using the doubly labeled water method, an isotope-based technique that looks at the difference between the turnover rates of the hydrogen and oxygen of body water as a function of carbon dioxide production.
The primary endpoint of the study was energy balance measured by body weight. Overall, the researchers found that energy expenditures and total weight loss were the same for the morning-loaded and evening-loaded diets. The subjects lost an average of just over 3 kg (about 7 pounds) during each of the four-week periods.
The secondary endpoints were subjective appetite control, glycemic control, and body composition. The participants reported that their appetites were better controlled on the days they ate a bigger breakfast and that they felt satiated throughout the rest of the day.
One limitation of the study is that it was conducted under free-living conditions rather than in the lab. Additionally, certain metabolic measurements were available only after breakfast and not after dinner.
As we can see, these results demonstrate that consuming loaded calories in the morning is not linked to weight loss, but improves the appetite through the day.
Further studies are needed to explore mealtime effects on various population groups and with greater manipulation of meal timing. In this population, morning-loaded feeding is likely to improve weight-loss success through behavioral adaptations as a result of greater suppression of appetite across the day.
Leonie C. Ruddick-Collins, Peter J. Morgan, Claire L. Fyfe, Joao A.N. Filipe, Graham W. Horgan, Klaas R. Westerterp, Jonathan D. Johnston, Alexandra M. Johnstone, (September 9, 2022). Timing of daily calorie loading affects appetite and hunger responses without changes in energy metabolism in healthy subjects with obesity. Cell Metabolism: Science Direct. Retrieved from : https://www.sciencedirect.com/science/article/pii/S1550413122003448?via%3Dihub
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