Breakfast is consistently cited as the most important meal of the day. In the world of undergraduate nutrition, it is constantly stated by my peers that it is either generally unhealthy to skip breakfast or that breakfast has some special ability to “jump-start” your metabolism and transform you into a metabolic furnace for the rest of the day. Some can even be quoted reporting that a subject may be failing to lose weight because they skip breakfast. Per usual, rather than accepting this dogma, I aim to unravel the validity of these claims through the scientific literature.
To begin with, it’s important to have a definition of what exactly breakfast is. While this definition may vary from person to person, the “first meal of the day, eaten before or at the start of daily activities (e.g., errands, travel, work), within 2 h of waking, typically no later than 10:00 in the morning, and of an energy level between 20 and 35% of total daily energy needs” is accepted as an academic standard (1).
Within the realm of nutrition research, many have connected skipping breakfast with increases in BMI (1). Likewise, many countries, such as the United States and the United Kingdom, have linked skipping breakfast with an increased risk of obesity (1). The important thing to remember about these viewpoints is that they are correlations rather than facts. It could be observed that the vast majority of healthy individuals eat breakfast, but that doesn’t mean they are at a healthy body weight because they eat breakfast. This population tends to also exercise, monitor their body weight, and are cognizant of portion sizes, all of which are major contributing factors to good health. On a related note, many overweight and obese individuals might be reported skipping breakfast. This does not mean skipping breakfast causes obesity. It could simply be a strategy implemented by many overweight and obese people to lose weight.
The theory proposed to support skipping breakfast leads to increases in body weight states that when people skip breakfast, they report higher levels of hunger and this leads to an overconsumption of calories at subsequent meals. Fortunately, there has been direct research conducted to test the validity of this hypothesis.
What the Direct Research Says
In a paper titled “Effect of skipping breakfast on subsequent energy intake,” two studies were reviewed. The first study examined the effect of skipping breakfast on the amount of energy consumed at a buffet lunch. Three groups were used for this experiment. One group skipped breakfast, the second group was given a high-fiber breakfast, and the third group consumed a low-fiber high-carbohydrate breakfast. Each subject participated in all three groups over the course of the study. This is referred to as a crossover design. At the conclusion of the study, while the group that skipped breakfast consistently reported higher levels of hunger at lunch, they did not have a statistically different energy intake at lunch compared to their energy intake when they also ate breakfast (2). When total energy intake was measured after breakfast and lunch, the average amount of calories consumed when eating the low-fiber high-carbohydrate breakfast was ~955 kcal, ~930 kcal when a high-fiber breakfast was consumed, and ~600 kcal when breakfast was skipped (2). In the end, skipping breakfast did not result in the compensation of calories at lunch.
In the second study this paper looked at, the effect of skipping breakfast on energy consumed throughout the rest of the day was analyzed. This study featured two groups (one skipped breakfast the other did not) in a crossover design. After breakfast was served or not served, food intake was measured after lunch, after mid-afternoon snack, after dinner, and after late-night snack. In the end, the results showed a slight increase in calorie consumption at lunch to compensate for skipping breakfast, but at the end of the day, despite reports of increased feelings of hunger after skipping breakfast, when participants skipped breakfast they consumed 450 calories fewer per day than when they ate it (2).
Another study with a crossover design titled “Effects of eating breakfast compared with skipping breakfast on ratings of appetite and intake at subsequent meals in 8- to 10-y-old children” found similar results. Subjects showed similar energy intakes at lunch after consuming breakfast (634 +/- 50 kcal) compared with after skipping breakfast (593 +/- 50kcal). The researchers ultimately found that when subjects ate breakfast, they consumed 362 more calories over the course of the day, which led to the participants exceeding their estimated energy requirements by approximately 20 percent (3).
Lastly, in the National Weight Control Registry, an organization created to investigate the characteristics and behaviors of individuals who have been successful at achieving their goal of losing weight and keeping it off long-term, a study was conducted to dissect the number of participants in the group who eat breakfast and if they have been more successful at losing weight and keeping it off than their breakfast skipping counterparts (4). Over 2,900 participants were included and this broke down into 314 subjects who did not consistently eat breakfast, and a whopping 2,645 that did. After analyzing the results, the researchers found there was not a significant difference in amount of weight loss, duration of weight-loss maintenance, or self-reported energy intake between groups (4).
A Side Note
While the main goal of this article is to examine the hypothesis that skipping breakfast leads to an overconsumption of calories at subsequent meals, for the sake of completeness, I would like to further disprove that breakfast has any significant metabolic effects by looking at another feature of calorie balance – energy expenditure. Sure, eating breakfast might not result in an overconsumption of calories at future meals, but does eating breakfast result in more total energy expended over the course of the day than when it is skipped? Probably not. A paper titled “Effect of breakfast skipping on diurnal variation of energy metabolism and blood glucose” found that there were no differences in 24-hour energy expenditure, resting metabolic level, or food-induced thermogenesis when subjects ate or skipped breakfast (5).
Further Beating the Dead Horse… Some Indirect Research
If breakfast had any inherent metabolism-enhancing effects, then the recently popularized diet, intermittent fasting (time-restricted feeding), would be inferior to its dietary counterparts because it typically features skipping breakfast.
As an aside, while in the realm of social media, having a limited window of time to eat is known as intermittent fasting, in the scientific literature it is known as time-restricted feeding. Intermittent fasting is an umbrella term which includes time-restricted feeding, alternate-day fasting which involves alternating between ad libitum eating and “fasting” days consisting of a single meal containing approximately 25% of daily calorie needs, and whole-day fasting which features 1-2 days of complete fasting per week plus ad libitum eating on the other days (6).
On to the time-restricted feeding research….
In a study titled “A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults,” the researchers compared the differences between 1 meal per day and 3 in a crossover design. The 1 meal per day or “meal skipping” group ate the same daily allotment of food as the 3 meal per day group, but did so in a 4-hour eating window in the early evening as opposed to spread out over the course of the day. The results showed that the subjects’ weight and body fat mass were lowered when they ate 1 meal per day but not when they ate 3 (7).
The authors proposed that this could be explained by a slight deficit of 65 kcal per day in the 1 meal per day group (7). Ultimately, this research shows that 3 meals compared to 1 meal per day is not metabolically superior, or that eating breakfast followed by another 2 meals evenly spaced out over the course of the day is not better than eating 1 meal in the early evening for weight loss. Another nice feature of this study is that physical activity was measured. The results reported that there was no significant difference in physical activity when either 1 meal or 3 meals were consumed per day (7).
In another study titled “Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males,” 34 subjects were randomly assigned to either a normal diet or time-restricted feeding group. The time-restricted feeding group consumed their energy needs in an 8-hour period, specifically, between 3 meals at 1 p.m., 4 p.m., and 8 p.m. The normal diet group consumed their 3 meals at 8 a.m., 1 p.m., and 8 p.m. The specific calorie distribution was assigned by a nutritionist and was based on the reported daily intake of each subject (8). After 8 weeks, the time-restricted feeding group showed a greater decrease in fat mass compared to the normal diet group (8).
I suspect that the time-restricted feeding group was misreporting their calorie intake. It is likely the subjects were over-reporting their calorie intake as a result of being unable to consume the same amount of food they were previously eating in a much shorter window of time. This would provide further insight into the potential positive impact of time-restricted feeding on weight loss. Perhaps more importantly though, this study shows foregoing the typical “breakfast” period and waiting until 1 p.m. to consume your first meal does not impact your ability to lose weight.
If you’re not hungry in the morning and would prefer not to eat then don’t. There is no magical effect to consuming breakfast, especially in regards to weight loss. As long as total calories and protein are equated, it doesn’t matter how many meals you consume or at what times you consume them, if you are in a calorie deficit you will lose weight. Another practical consideration, as evidenced by the research, is that if you are trying to lose weight, it may be a benefit to skip breakfast, or simply set a limited time range for when you allow yourself to eat. Under both conditions, the research tends to report a subconscious decrease in total daily energy consumption.
- Zilberter, T., & Yuri Zilberter, E. (2014, June 03). Breakfast: To Skip or Not to Skip? – PubMed Central (PMC). Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4042085/
- Levitsky, D. A., & Pacanowski, C. R. (2013, July 02). Effect of skipping breakfast on subsequent energy intake. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/23672851
- VE Kral, T., Whiteford, L. M., Heo, M., & Faith, M. S. (2010, November 17). Effects of eating breakfast compared with skipping breakfast on ratings of appetite and intake at subsequent meals in 8- to 10-y-old children. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3021425/
- Wyatt, H. R., Grunwald, G. K., Mosca, C. L., Klem, M. L., Wing, R. R., & Hill, J. O. (2002, February 10). Long-term weight loss and breakfast in subjects in the National Weight Control Registry. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/11836452
- Kobayashi, F., Ogata, H., Omi, N., Nagasaka, S., Yamaguchi, S., Hibi, M., & Tokuyama, K. (2014, May/June). Effect of breakfast skipping on diurnal variation of energy metabolism and blood glucose. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/24847666
- Tinsley, G. M., & La, P. M. (2015, October). Effects of intermittent fasting on body composition and clinical health markers in humans. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/26374764
- Stote, K. S., Baer, D. J., Spears, K., Paul, D. R., G Keith Harris, Rumpler, W. V., . . . Mattson, M. P. (2009, February 20). A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2645638/
- Moro, T., Tinsley, G., Bianco, A., Marcolin, G., Francesco Pacelli, Q., Battaglia, G., . . . Paoli, A. (2016, October 13). Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Retrieved January 17, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5064803/