Researchers from the University of Aberdeen have explored how the timing of the main meal interacts with metabolism and weight control. Their findings suggest that the clock behind meals does not change how the body metabolizes energy, yet starting the day with a substantial breakfast can make weight loss more achievable in everyday life. This work is reported in Cell Metabolism and adds nuance to the popular belief that meal timing alone drives body weight outcomes.
The study enrolled healthy adults who were overweight or obese, comprising 16 men and 14 women. Participants were randomly assigned to consume the larger portion of their daily calories in either the morning or the evening for a four week period. The diet was designed to be calorically limited while maintaining a consistent macronutrient balance of roughly 30 percent protein, 35 percent carbohydrates, and 35 percent fat. After the initial four weeks, participants paused for a week, then switched the schedule so those who ate most in the morning then shifted to consume more later in the day, and vice versa. This crossover design allowed each person to serve as their own control, strengthening the reliability of the comparison between meal timing strategies. The study genreically tracked energy use with a dual isotope water labeling method to quantify total daily energy expenditure, providing a robust measure of metabolic response during each phase of the experiment. Citation: University of Aberdeen research team, Cell Metabolism, study on meal timing and energy expenditure.
Across the two four week periods, energy expenditure and weight loss showed no meaningful difference between the morning-biased and evening-biased groups. On average, participants shed a little over three kilograms during each four week period, demonstrating that meal timing, in the context of a calorie-restricted plan, did not alter the overall pace of weight reduction. This aligns with the notion that total energy balance remains the dominant driver of weight change over short to medium time frames, regardless of when meals occur during the day. Citation: University of Aberdeen research team, Cell Metabolism, study on energy expenditure and weight loss outcomes.
However, participants reported practical benefits linked to a hearty breakfast. On days when a substantial morning meal was consumed, many participants described better appetite control and a feeling of fullness that carried through the day, reducing the likelihood of late morning or afternoon cravings. While circadian biology did not produce a faster or slower rate of weight loss in a controlled setting, the real-world experience suggests that a robust breakfast can support adherence to a calorie plan and improve daily energy balance. In other words, a well nourished morning start may help people maintain momentum when translated from a research protocol into everyday life. Citation: University of Aberdeen research team, Cell Metabolism, insights on appetite regulation and real world weight management.