The Reason Why a Well-Balanced Breakfast Helps to Prevent Weight Gain


  1. A background of the importance of breakfast in recent years
  2. How eating breakfast affects weight management? My thoughts
     (1) A well-balanced breakfast can help prevent gaining weight
     (2) Lightening your breakfast and lunch makes you more likely to gain weight 
     (3) Skipping breakfast makes it easier to gain weight
  3. Conclusion

In the previous article, I introduced the concepts of a "biological clock," and “chrono-nutrition,” but if you have not read them yet, please read the following article first.
This time, I am going to state my own thoughts on how eating breakfast affects weight management concretely by my intestinal starvation theory. 

[Related article]  
"When to Eat" Is Important, but It Should Be Paired With "What to Eat"


1. A background of the importance of breakfast in recent years

(1) Observational evidence suggests that there is an association of breakfast eaters with lower body weight (lower BMI) compared to non-breakfast eaters.

However, there is little causal evidence to support this conjecture. Regular breakfast intake is associated with health-promoting behaviors, implying that breakfast intake may be a proxy for health-promoting behaviors. The association in observational studies may reflect a "healthy user bias."[1]

(2) Short-term studies highlight physiological mechanisms by which breakfast may affect body weight, such as appetite, energy expenditure (metabolism), and fat oxidation. However, whether the proposed physiological mechanisms translate to a long-term effect on energy intake and body weight remains unclear[2].

(3) Some hypotheses with regard to breakfast intake and lower body weight speculate that breakfast intake is important for regulating subsequent energy intake. Some studies have shown that skipping breakfast results in higher energy intake at lunch. On the other hand, others suggest that skipping breakfast may not compensate for a need for increased energy intake later in the day, resulting in a decrease in total daily caloric intake relative to when breakfast is consumed[3].

(4) Public health authorities commonly recommend breakfast intake to reduce obesity.
A randomized controlled trial (RCT) in the U.S. in 2014 tested the effectiveness of a recommendation to eat or skip breakfast on weight loss. Approximately 300 overweight or obese adults who trying to lose weight were randomly assigned to one of three groups (control, breakfast, or no breakfast), and the effect of treatment assignment on weight loss was tested in a free-living setting for 16 weeks.

However, this trial showed no effect of a recommendation to eat or skip breakfast on weight loss[4]. In this RCT, the total daily caloric intake, which foods to combine at breakfast, and the timing of meals, etc. were considered free and not specified.

(5) A review of the scientific literature up to 2006 on the "relationship between breakfast habits and body weight and chronic disease risk," analyzed through a MedLine search, pointed to the following issues: Many observational studies have found that breakfast frequency is inversely associated with obesity and chronic disease, but observational studies have some limitations. Only four relatively small, short-term randomized trials have examined breakfast intake and body weight or chronic disease risk, with mixed results.
Measurement of breakfast frequency for the most part is self-reported and subject to each individual's idea of what constitutes breakfast. Therefore, it is possible that the luck of a universal definition for breakfast and measurement of the breakfast has led to conflicting results in some cross-sectional and prospective studies assessing the association between breakfast and obesity and chronic disease risk [5].

2. How eating breakfast affects weight management? My thoughts

I think the concept of “chrono-nutrition” is very important in this day and age, but there are many aspects that cannot be explained by metabolism or hormones alone. 

Based on the conventional belief that obesity is caused by "overeating and/or lack of exercise," it does not make sense that people who eat breakfast are associated with lower body weight despite consuming more calories per day than those who skip breakfast. Many researchers try to explain the long-term positive energy effects by looking at how energy expenditure changes over time when breakfast is consumed or skipped, but I think this explanation has limitations.

I believe it makes more sense to explain this with my intestinal starvation theory. Below, I would like to explain it in three different patterns.


(1) A well-balanced breakfast can help prevent gaining weight

Breakfast is the start of the day, and when you eat breakfast, your resting gastrointestinal tract becomes active.

If you eat a variety of food at that breakfast, such as dairy products, fibrous vegetables, seaweed, legumes, and protein, you can prevent intestinal starvation because undigested food will remain in your intestines for around ten hours or so (this is because our intestines are seven to eight meters long). 

Three balanced meals a day

Also, if you eat well both at lunch and dinner, you are less likely to gain weight (meaning that your base weight does not go up), since there is some undigested food remaining over a twenty-four-hour period in your gastrointestinal tract. 

Japanese breakfast

(Typical Japanese breakfast we used to have)

This is the reason why people who are originally slim or medium-sized and have this kind of lifestyle are unlikely to change their body shape throughout their lives, even if they eat without worrying about calories.

However, keep in mind that those who are already overweight will not necessarily lose weight just by eating breakfast (since their base weight is already high).

(2) Lightening your breakfast and lunch makes you more likely to gain weight

On the other hand, breakfast can be fattening (in the sense that it increases one's base weight) even if one eats it. It is a so-called inverted triangle-type diet, in which breakfast and lunch are light (one might even skip lunch) and dinner makes up for the missing nutrients and calories.

light breakfast and lunch

For example, if you just have a light breakfast (a piece of bread, coffee, mashed potatoes, and ham) in the morning, and a rice ball, hamburger, or instant noodles, etc. for lunch, it is easy to induce a intestinal starvation state before dinner, contrary to the situation described in (1) above.

When the gastrointestinal tract becomes active after breakfast, you usually go to the bathroom, and when you do, the only food left in your stomach is what was eaten at breakfast (in this case, mainly carbohydrates and easily digestible protein). 

If lunch is also a simple carbohydrate-based meal and lacks fiber and other nutrients, all the food in the intestines will be digested by dinner, which makes it easier to develop a state of intestinal starvation. 

In short, if breakfast is well-balanced with choices from the various food groups, you are less likely to gain weight, but if it is a simple and unbalanced one, there is a good chance you will gain weight over the long haul. 

Therefore, it is not only a recommendation to eat breakfast, but also to eat a well-balanced one that includes fibrous vegetables, protein, and dairy products, etc.

(3) Skipping breakfast makes it easier to gain weight

People who do not eat breakfast may be associated with a nocturnal lifestyle (late night dinner or eating light meals before bed). In short, the main reason for them skipping breakfast may be a lack of appetite or a lack of time to eat.

Not everyone will gain weight if they skip breakfast, but based on my theory, if some conditions are met and overlapped, it makes one more likely to gain weight. The biggest issue is simply a matter of "what to eat at lunch and dinner" and the interval between meals.

Eating only two meals a day makes the meal intervals longer. If you finish dinner at ten p.m., you will not eat for almost fourteen hours until the next day, at noon. Skipping breakfast makes you hungry, so in Japan, people tend to eat lunch with many carbohydrates (rice or noodles) and some meat. Some of them are satisfied with just being full, and their meal may lack fiber and other nutrients. 

hearty meal at lunch

However, since they have not eaten breakfast, all they have in their gut is that meal at lunch. If they don’t eat until eight or nine p.m. in that state, they are likely to induce intestinal starvation (a state where everything is digested) little by little, and their base weight may go up over time.

Some experts also point out that skipping breakfast and eating a carbohydrate-dense meal when hungry can cause blood glucose levels to spike, leading to high insulin secretion.

This may be true, but in any case, the combination of a "prolonged feeling of hunger" and an unbalanced diet leaning towards carbohydrates and with a lack of vegetables, is likely to make people fat, even if their caloric intake is not that much.

You can prevent intestinal starvation by doing the following: if you don't have time to eat in the morning, at least drink some milk, and eat a balanced lunch with a smaller amount of carbohydrates. And if you have to eat dinner late, eat something such as milk, chocolate or nuts, even around five p.m.

3. Conclusion

I think what has confused researchers over the years is “whether or not breakfast itself is directly associated with reduced risk of obesity and chronic disease? In other words, is there a causal link there?," and my thoughts, based on the intestinal starvation theory, are as follows:

(1)First, I think it is quite possible that people who usually eat breakfast have other healthy lifestyle habits.

For example, they may eat three times a day regularly, with a well-balanced diet that includes vegetables, dairy products, and protein, etc. throughout the day. They may also exercise religiously, get good quality sleep, and live in accordance with their circadian rhythms. 

On the other hand, those who tend to skip breakfast may have a nocturnal lifestyle and poor habits in terms of drinking, smoking, sleeping, and dietary balance.

In short, there might be some confounding factors associated with breakfast.

(2)However, as explained in section [2] above, eating a well-balanced breakfast early in the morning, will prevent intestinal starvation being induced by allowing undigested food in the gastrointestinal tract to remain around ten hours or so. Other health benefits of having undigested food such as fiber and fat in the gut, would include reducing blood sugar spikes and regulating appetite. 

On the other hand, an unbalanced breakfast skewed towards easily digestible carbohydrates, proteins, and processed foods, etc. can lead to weight gain, so I do not believe that "breakfast" itself has the effect of deterring weight gain. I’m certain that it is "which foods to combine" at breakfast that matter. (In this regard, intestinal starvation may also be a confounding factor.)

I personally think that if you don't want to eat breakfast, that's fine, but isn't it important to eat lunch and dinner in a balanced manner with a moderate amount of carbohydrates to maintain good health and reduce the risk of obesity?

(3)Also, in my theory, the problem of obesity implies a higher base weight, and 
 I believe just eating breakfast does not necessarily lower the base weight of a person who is already overweight. In other words, even if a randomized intervention to "eat or skip breakfast" were conducted in obese or overweight people as in a 2014 U.S. randomized controlled trial (RCT), it may be difficult to demonstrate the benefits of breakfast. But, this does not mean that breakfast itself is meaningless.


[1]Flanagan A, et al. Chrono-nutrition: From molecular and neuronal mechanisms to human epidemiology and timed feeding patterns. J Neurochem. 2021 Apr;157(1):53-72. doi: 10.1111/jnc.15246. Epub 2020 Dec 10. PMID: 33222161. 

[2][3][4]Dhurandhar EJ et al. The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial. Am J Clin Nutr. 2014 Aug;100(2):507-13. doi: 10.3945/ajcn.114.089573. Epub 2014 Jun 4. PMID: 24898236; PMCID: PMC4095657.

[5]Timlin MT, Pereira MA. Breakfast frequency and quality in the etiology of adult obesity and chronic diseases. Nutr Rev. 2007 Jun;65(6 Pt 1):268-81. doi: 10.1301/nr.2007.jun.268-281. PMID: 17605303.