If you want to lose weight: "Eat breakfast like a king, lunch like a prince, and dinner like a pauper." We’ve all heard this phrase at least once, just before we “dig in” to a full plate of dinner after a tiring day.
If this belief could be expressed as a question, it would be: "Does a plate of pasta eaten at lunchtime have fewer calories than a plate eaten in the evening?" The answer, though self-evident, does not seem quite so simple to most people. So, do calories consumed at night lead to greater weight gain? In other words, should breakfast always be the heartiest and most important meal of the day, with subsequent meals becoming smaller?
Before we answer these two questions, let’s understand that our body could be likened to an energy reservoir. Every person’s “tank” is unique; it varies in size and capacity, which corresponds to the calories —that is, the food—that the human body needs at rest to perform its basic functions, such as breathing or digestion. Simply put, this “reservoir” represents the minimum number of calories we need each day—that is, our basal metabolic rate.
Based on the above, anything we consume that provides calories fills our “tank” to a greater or lesser extent. So, to lose weight, all we need to do is keep the level in our “tank” just slightly below its capacity. This actually means that if we compare two people, one of whom eats as healthily as possible, eats frequently, but in large portions, while the other eats just one meal a day—consisting of a pizza and a crepe—it’s the second person who will actually lose weight! And that's because he didn't fill up his energy "reservoir."
But be careful! The weight loss achieved is unhealthy, on the one hand because the body does not receive the nutrients it needs to perform its functions, and second, because they do not lose harmful fat mass, but rather the necessary muscle mass.
Of course, let’s not forget that the level of our tank is also determined by our activity. Whenever we move, exercise, or even think, our bodies use calories as “fuel.” So our physical activity also contributes to weight loss! However, it is not the only one, as many people believe.
Returning to our questions, it is now clear that at the end of the day—or, more accurately, at the end of the week—our body, based on its needs, takes stock of the day. Its composition depends on the quantity and quality of the food we give it. He isn't so interested in which day or time of the week we ate pasta, but he is interested in whether that pasta "overflowed" the tank and whether there were other days when the tank was "full" or overflowing reservoir over the course of the week.
As for the second question, that's where things get a little more personal! We need to define what “morning” means and what “important” means (that is, important for what reason). If the question is about an athlete who trains hard in the morning and therefore needs plenty of energy, then the answer is that breakfast is an integral part of his routine. However, if the goal is simply to lose weight or, more generally, to adopt healthy habits, then the importance of breakfast depends on us.
In the first case, skipping breakfast leads to a shortfall in energy intake at the start of the day. Whether this deficit is maintained depends on the amounts of the rest of our food intake throughout the day. Therefore, if any of us decide that skipping breakfast works for us, this is an important tool for achieving a calorie deficit. But even someone who wakes up and can't function unless they eat something can still lose weight or maintain a healthy lifestyle. This is also confirmed by scientific studies conducted on both obese and normal-weight individuals, which showed that weight loss resulting from an isocaloric calorie restriction was the same regardless of whether they ate breakfast or not.
In contrast, ardent advocates of breakfast as a means of weight loss cite other studies, which suggest that people who skip breakfast have elevated levels of ghrelin, a hormone that regulates appetite. This leads to a significant increase in participants’ feelings of hunger throughout the rest of the day, causing them to consume larger amounts of food, thereby “filling up” their calorie “reservoir” to a considerable extent and slowing their weight loss compared to those who have eaten breakfast. However, as already mentioned, this outcome depends significantly on how each person manages their daily life. Furthermore, another argument is that it has been shown that eating at times that are biologically unfavorable for energy metabolism is associated with a slightly faster rate of weight gain. This is because energy balance is best maintained when the majority of caloric intake occurs in the morning or early afternoon, since our bodies typically use energy more efficiently rather than storing it. It is worth noting, of course, that every organism is unique, and not all organisms utilize the energy they take in the same way. That’s why there’s no need for absolute rules!
In closing, the broad field of nutrition and health is rife with misconceptions and absolute statements. There is no one-size-fits-all answer. It would be good for everyone to discover their own “most important meal” and the diet that suits their goals and habits. That is why, when we are bombarded with information, we must not accept it uncritically, nor should we restrict ourselves to strict rules, such as eating only one piece of fruit in the evening before the clock strikes 8:00 p.m. Instead, let’s listen to and respect our bodies’ true needs!
Bibliography
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Hall, K. D., Schoeller, D. A., & Brown, A. W. (2018). Reducing calories to lose weight. Jama, 319(22), 2336–2337.
Liu, D., Huang, Y., Huang, C., Yang, S., Wei, X., Zhang, P., ... & Zhang, H. (2022). Calorie restriction with or without time-restricted eating for weight loss. New England Journal of Medicine, 386(16), 1495–1504.