|We know just one thing about breakfast: Everyone believes it was good for you :-)|
Now, aside from the fact that I know that some of you are not willing to spend the time to read the full-text of the paper, I would not even be allowed to put it up for you to download it. In view of the fact that I also feel that I have one or another thing to add to the discussion, I decided to take compile a brief summary of what I believe are the most important points in Brown et al. 's excellent paper.
I already hinted at the main criteria of biased reporting the researchers used in the title of today's SuppVersity article:
- For the average Joe, scientific bias is only an indirect problem. For him statements likeBiased interpretation of one’s own results. Specifically in the abstracts, findings in favor of the notion that having breakfast will help preventing obesity are emphasized, while findings that are not in line with this hypotheses are either mentioned only as a side-note or simple left out.
- "The fact is, when you’re trying to lose body fat, you can’t skip breakfast." (Dr. Oz),
- "In fact, skipping breakfast actually increases your risk of obesity." (Mayo Clinic),
- "Want to trim your waist? Try eating breakfast" (Academy of Nutrition and Dietetics),
Our constant exposure to statements like these from "authorities" and those people in our surrounding who listen to what these "people in the know" say, has the concept of the "healthy" and "anti-obesogenic" breakfast engrained so deeply into our brains that even scientists apparently can't escape the subconscious pro-breakfast bias.
- Improper use of causal language in describing one’s own results. Even saying "breakfast has a protective effect against diabetes", would in 99% of the cases qualify as improper use of causal language and that's not just because there is no "may" or "suggest" in here, but simply due to the fact that neither cross-sectional nor longitudinal observational studies (which is what we are dealing with mostly) are actually able to determine causal relationships.
- Misleadingly citing others’ results. Brown et al. identified a pretty impressive example for this practice, when they analyzed the available literature on the matter. It's a study by Schlundt et al. that observed a borderline significant interaction between being assigned to a breakfast condition that differed from the subjects' habitual one, but failed to identify a significant main effect of breakfast consumption on the outcome of their controlled weight loss trial. In other words: "Subjects who were assigned to change from their baseline breakfast frequency lost more weight than did subjects assigned to continue their baseline breakfast frequency" (Brown. 2013). Despite the fact that this does obviously not warrant the conclusion that that breakfast eating would promote weight loss, Brown et al found that of the 46 English language articles that cited Schlundt et al in the context of the proposed effect of breakfast on obesity (PEBO) only 17% of articles cited the results accurately. 29 of them "abused" the results in favor of the "breakfast helps weight loss"-hypothesis and a single article used Schlund et al.'s results to argue against its benefits, which is obviously just as unwarranted.
- Improper use of causal language in citing others’ work. Basically not different from what I have already explained in the context of the interpretation of one's own results, the example Brown et al. use in their paper is a 2002 study by Wyatt et al. that identified a co-occurance (which has not the slightest causal element in it) of weight-loss maintenance and breakfast eating makes it quite clear that it's not just the supplement industry that loves to mask co-occurrences as causal relationships. Only 29% of the papers discussing the results of Wyatt et al. got the difference right, 26% turned it into an association (which was not even tested) and 22% went even one step further and talked about some sort of causal relationship being involved here.
Now, what's actually true? What can you believe?
As Brown et al. point out, "there have been very few RCTs that investigated breakfast and weight change." (Brown. 2013) Consequently, researchers' overview of the currently available literature does not allow for a definitive answer to the litmus question "Is skipping breakfast good or bad for you?"
|Figure 1: Randomly selected long(er) term studies on weight gain / loss of having / not having breakfast.|
|Food timing can also influence our biological clock | learn more|
Incidentally, intermediate endpoint studies would support the notion that behavioral mechanisms play a much larger role in the etiology of the purported link between breakfast consumption and obesity. The often heard hypothesis that having breakfast will reduce subsequent energy intake in the course of the day and thus result in an overall reduced food intake, however, is not supported by the currently available evidence.
|Figure 2: Selection of controlled studies investigating the effect of breakfast eating / skipping on total energy intake.|
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