Is Breakfast Really the Most Important Meal of the Day?

Most of us have grown up hearing the old adage that breakfast is the most important meal of the day and health experts have been warning for years that skipping breakfast can lead to weight gain. Yet, with the popularity of intermittent fasting on the rise, the authenticity of this piece of nutrition advice has been called into question. As such, a trip to PubMed, and a closer look at the scientific evidence on this nutrition conundrum, is warranted.

Breaking the Fast

The origins of breakfast are fascinating and well worth a read (check out this excellent Atlantic article for more). Perhaps the most interesting take away is that health and nutrition were not the predominant influencers on the decision to eat breakfast. In fact, class, religion, and culture were the primary motivators. In the middle ages, breakfast was shunned by most since it was viewed as a gluttonous act that slighted God (although small meals were permitted for some out of caloric necessity; 1). According to experts, breakfast did not become popular and normalized until chocolate, primarily consumed as a beverage, was introduced to Europe in the 1600s (1). And with time and social normalization, the morning meal gradually shifted from one of luxury to one of expectation.

The Scientific Stance on Breakfast

When debating nutrition in the present tense, it’s tempting to fall back on our ancestors and use their diet to justify our choices of now. And sure, while human physiology changes fairly slowly, using our ancestors as a reference for health – when the average lifespan of someone living in 17th century Europe was just 35 years (2) – is clearly flawed. Instead, we need to look at what research has to say about the role of breakfast on weight status in today’s food environment.

Breakfast and Weight Outcomes

Randomized controlled trials (RCTs) are a type of study where participants are randomly assigned to an intervention or a control group. In the hierarchy of scientific evidence, RCTs are considered high-quality, sitting just below the top-rated systematic reviews and meta-analyses (3). As such, to find out more about breakfast’s role on weight status, this is the type of study I’m going to report on.

The results of a narrative review (4) that included 3 RCTs found that eating breakfast versus skipping breakfast had no significant influence on weight in obese/overweight adults (5, 6) or children (7) after 12 and 16 weeks, respectively. However, there were many factors not considered, such as the energy-density of the meal and its macronutrient composition, that make it difficult to say with certainty that breakfast has no effect on weight. To better determine the role of breakfast on weight outcomes, attention to these details is needed.

Breakfast Size/Composition and Weight Outcomes


The impact of a breakfast high in protein on weight loss outcomes is unclear. Some studies suggest that a high-protein breakfast, compared to a lower protein breakfast, can mitigate gains in fat mass among overweight/obese adolescents (8) but may have a negligible impact on actual weight loss (9). One study showed that among obese adults following a calorie-restricted diet, a large breakfast with high protein (600 calories, 60 g carbohydrates, 45 g protein, 20 g fat), compared to a smaller breakfast (200 calories, 10 g carbohydrates, 30 g protein, 16 g of fat), resulted in significantly greater weight loss at 32 weeks (difference of 37.7 lbs), but not at 16 weeks (10). Thus, it seems that protein could have a positive influence on weight loss, although additional studies are needed.


A 12-week RCT carried out in overweight adults where a low or high-fibre breakfast (containing 3 g or 28 g of fibre, respectively) was provided saw a small, but statistically significant 2% greater weight loss among the high-fibre group (11). Furthermore, the high-fibre group had greater reductions in BMI, waist circumference, fat mass, and percentage body fat compared to the low-fibre group.

Breakfast Size

In addition to the study mentioned above, where both protein and calories were increased in the morning, two other studies carried out among obese/overweight woman found that consuming a larger breakfast (700 calories vs. 200 calories; 12) or eating 70% of total daily calories in the morning and at lunch (compared to only 55% of total daily calories; 13) resulted in significantly greater weight loss, BMI, waist circumference, and body fat over 12 weeks.

Conclusion (?)

Drawing firm conclusions from the above studies is challenging due to the relatively short-period of time that the studies were carried out (i.e. 12 weeks), the lack of control of other confounders (such as activity and macronutrient distribution), and problems with the studies’ design (i.e. not all studies were RCT trials). Nevertheless, it seems possible that a pattern of intake that favours greater calorie intake in the morning period (with the addition of protein and fibre) could be helpful in achieving weight loss outcomes.

Practical Recommendations

In my practice, I generally advocate for the consumption of breakfast as I’ve noticed that breakfast skippers often compensate for missed calories later in the day through late-night, high-calorie munchies. That said, there is a subgroup of individuals who generally feel better delaying the morning meal, who do not compensate by overeating later in the day, and are still achieving their health and wellness outcomes.

When it comes to eating, there really is no “one size fits all” approach. If you’re curious to see how breakfast affects your health and calorie intake, take some detailed notes in your Cronometer account and compare your nutrition reports when you eat breakfast versus skip breakfast (to gather enough data, you may wish to carry this experiment out for ~3 months). If you are eating daily breakfast, the most important considerations are to include a) sufficient calories (I usually recommend aiming for at least 20-25% of your calorie needs) and b) adequate protein (e.g. 20-30 g) and fibre (10-15 g). You may also notice that including greater amounts of soluble, compared to insoluble fibre, enhances daytime satiety.


Susan Macfarlane is a Registered Dietitian Nutritionist utilizing to help run a busy private practice in Ontario, Canada and blogs regularly for



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  9. Wang S, Yang L, Lu J, Mu Y. High-Protein Breakfast Promotes Weight Loss by Suppressing Subsequent Food Intake and Regulating Appetite Hormones in Obese Chinese Adolescents. Horm Res Paediatr 2015; 83:19–25. Abstract available from:
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  11. Hu X, Gao J, Zhang Q, Fu Y, Li K, Zhu S, Li D. Soy fiber improves weight loss and lipid profile in overweight and obese adults: a randomized controlled trial. Mol Nutr Food Res. 2013 Dec;57(12):2147-54. Abstract from:
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