The current meta-analysis suggests that breakfast consumption increases total daily energy intake and bodyweight compared with breakfast omission. The extra calories consumed at breakfast do not appear to be fully compensated for later in the day.
These results go against what has been regularly promoted by many official nutritional guidelines, which encourage eating breakfast as one of the key strategies to maintaining a healthy weight. This recommendation is based primarily on observational data showing an association between breakfast consumption and lower weight and fat mass.
However, this association is confounded greatly by other habits of people who regularly eat breakfast, such as being more physically active, drinking less alcohol, and not smoking as much. Data from successful long-term weight loss maintainers, depicted in Figure 2, has shown that 78% eat breakfast daily, and that 90% eat breakfast at least four times per week. Yet, there were no differences between breakfast eaters and skippers for the degree of weight loss or duration of weight loss maintenance.
Overall, it is likely that breakfast is commonly part of a healthy lifestyle that promotes weight loss or the maintenance of a normal BMI, but it isn’t the cause of either. When the effect of breakfast is directly tested (as in this meta-analysis), no positive effect on weight loss is seen.
One of the main arguments in favor of consuming breakfast for maintaining a healthy body weight has been the suggestion that it would reduce subsequent food intake during the day, and therefore prevent the consumption of excessive calories later in the day. As this meta-analysis shows, breakfast consumption does not lead to lower food intake later in the day and hence adds more energy to the daily diet. This effect seems to be consistent, as it was observed in six of the nine trials included that assessed this metric. Accordingly, other authors have observed that the absolute amount of calories consumed for breakfast are strongly and positively correlated with total daily calorie intake. Because of this, eating breakfast per se does not constitute a necessary intervention for promoting a caloric deficit conductive to weight loss.
On the contrary, it could even promote weight gain, given that it adds more energy to the daily diet, compared to skipping breakfast. This has important implications for obesity recommendations, as people associate eating breakfast with healthy eating patterns and start eating breakfast in attempts to adopt a healthy lifestyle.
In some cases, this strategy could backfire and promote weight gain. This has been shown in an RCT included in the meta-analysis, which found that breakfast consumption in women who regularly skipped breakfast led to an increase in daily energy intake (+266 kcal) and gained 0.7 kilograms (1.5 pounds) over four weeks, compared to the group who kept skipping breakfast.
A major strength of this meta-analysis is that it included only trials from high income countries, which reduces heterogeneity due to food availability under different economic or geographic situations. On the other hand, the analyzed RCTs only included adults without any disease besides being overweight or obese (such as diabetes, metabolic syndrome, etc.), so extrapolation to other populations such as children, adolescents, older people, those with chronic diseases or highly active people is not possible. In addition, the effects of different breakfast compositions were not assessed. Finally, the included studies only followed participants for a very short time (less than four months) and overall were of low quality. Also, it is conceivable that adaptations to breakfast in the long term include a reduction on calorie intake later in the day, and therefore, the weight-promoting effect is only observed in the short term.
In view of the overall high risk of bias, mediocre quality of the available research as a whole, and lack of assessment of breakfast composition or habits, higher quality evidence and adjustment for breakfast habits in future research could overturn these results in either direction down the road. So, while the evidence points toward breakfast helping with weight loss, it does so quite weakly. Higher quality evidence is needed to come to firm conclusions.
In contrast to what observational studies have suggested, this meta-analysis found that skipping breakfast does not increase bodyweight nor total daily energy intake. On the contrary, breakfast skipping reduces daily energy intake and bodyweight. This discrepancy might be explained by the fact that breakfast eaters also have other healthy habits that promote weight maintenance. However, the data that went into this meta-analysis is generally short-term and of low quality — longer and higher quality studies are needed.