There is an old saying in dieting that you should “breakfast like a king, lunch like a prince and dinner like a beggar” based on the belief that consuming most of your daily calories in the morning optimizes weight loss by making calories more efficient. to burn and fast. But according to a new study published Sept cell metabolismWhether a person eats their largest meal early or late in the day doesn’t affect the way their body metabolizes calories. However, people who ate their largest meal in the morning reported feeling less hungry later in the day, which could lead to easier weight loss in the real world.
“There are many myths about the timing of eating and how it can affect body weight or health,” said senior author Professor Alexandra Johnstone, an appetite control researcher at the Rowett Institute, University of Aberdeen, Scotland. “This is largely driven by the circadian rhythm field. But we in the diet have wondered how this could be possible. Where would the energy go? We decided to take a closer look at how the time of day interacts with metabolism .”
In this study, the researchers recruited healthy, overweight or obese subjects to control their diet and measure their metabolism over a period of time; 16 men and 14 women completed the study. Each participant was randomly assigned to eat either a morning- or evening-loaded diet for four weeks. The diets were isocaloric, with a balance of 30% protein, 35% carbohydrates and 35% fat. After a week-long washout period in which calories were balanced throughout the day, each participant switched to the opposite diet for four weeks. In this way, each participant acted as their own study control.
Throughout the study, the subjects’ total daily energy expenditure was measured using the double-labeled water method, an isotope-based technique that looks at the difference between the hydrogen and oxygen conversion rates 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 expenditure and total weight loss were the same for the morning- 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 larger breakfast and that they felt full for the rest of the day,” says Johnstone. “This can be very helpful in the real world, versus in the research environment we were working in.”
A limitation of the study is that it was conducted under free-living conditions rather than in the lab. In addition, certain metabolic measurements were only available after breakfast and not after dinner.
Johnstone notes that this type of experiment can be applied to the study of intermittent fasting (also called time-restricted eating), to help determine the best time of day for people following this type of diet to consume their calories.
The group plans to expand its research on the influence of time of day on metabolism by conducting studies similar to those described here in subjects working in shifts. It is possible that these individuals have different metabolic reactions due to the disruption of their circadian rhythms. “One thing that’s important to note is that when it comes to timing and diets, there probably isn’t going to be one diet that’s right for everyone,” concludes Johnstone. “Finding this out is going to be the future of diet studies, but it’s something that’s very difficult to measure.”
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