Sunday, October 27, 2013

"Breakfast Keeps You Lean" Myth or Mystically True: Hard To Tell With All the Bias, Highly Improper Language Use, Misleading Citations and Unwarranted Causal Implications

We know just one thing about breakfast: Everyone believes it was good for you :-)
Let me first point out that large parts of this article are based on ideas from recently published paper by Brown, Brown and Allison who wrote about the unwarranted and deep rooted believe that skipping breakfast was the first step on the royal road to obesity in a recent issue of the American Journal of Clinical Nutrition (Brown. 2013). Their hypothesis that the conviction that breakfast is the most important meal of the day was so strong that the analyses of experimental and epidemiological data will always fall in line with the (subconsciously) expected outcome, is so appealing that I do not want to deny you this information.

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 like
    • "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),
    or the Surgeon General's assertion "Eating a healthy breakfast is a good way to start the day and may be important in achieving and maintaining a healthy weight" are the real problem (examples from Brown 2013).

    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.
    Biased 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.
  • 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.
The biased, sometimes false reporting, as well as the focus on studies that were designed to produce the desired result "Breakfast is good for you!" must not hide the fact that we actually still don't know if eating breakfast will have beneficial, neutral or maybe even negative on our metabolism, body weight and body fat levels.

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.
I know that some of you will now jump at the results of those trials that suggest that skipping breakfast is beneficial, surf over to whatever "anti-breakfast"-facebook group they are in and start celebrating the corresponding articles as evidence that they've been right all along... don't do that! In view of the intriguing observations Schlundt et al. made in their previously cited stud, it may simply be that switching from one meal pattern to the other may have brought about the beneficial effects.
Food timing can also influence our biological clock | learn more
How simply changing the system may facilitate weight loss : You just have to look the success people have with the guru-esque "you must not eat"-approaches you will find plastered all over the Internet (and costly ebooks) - if your favorite foods are not on the "you are allowed to eat"-list (which is almost always the case with these 5-10 item lists), you will automatically lose weight (* it is important to point out that the beneficial weight loss effects do not depend on the "quality" of the system - you may switch from a bad diet to an even worse one - as long as you break with your habits and can't overeat on your favorite foods, you'll loose weight)
A similar effect as with the contemporarily increasingly popular "you must not eat this" diets will obviously also occur, if you are a breakfast eater who loves his tons of cereals and bagels or your truckloads of bacon and eggs. Once you simply skip on those, it's not very likely that you will compensate on other foods later in the day, so that it is not surprising if you lose weight - you simply consume less energy than before!

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.
Things look different for observational studies, though. The majority of these usually cross-sectional assessments of the temporary relationship of breakfast consumption and obesity, indicates that there is "a clear link between breakfast omission and excess weight" (Brown. 2013) - what these analyses don't tell us, though, is that this is a causal relationship.
" Cardio on Empty is Fatiguing. Fasting Without Exercise, However, is Nootropic" | read more
Bottom line: In the end, there are only three things we know for sure. There is a major bias in favor of a desirable (=preventive) effect of breakfast on obesity in the general public, the authorities and even among the scientists. This bias is reflected in the currently available literature in form of improper language use, misleading citations and unwarranted causal implications.

As long as we don't get rid of this built-in bias, we are left with a host of observational evidence, tons of flawed reviews and no answer to the (imho not even important) question whether you should or shouldn't have breakfast if you want to lose or maintain your current body weight.
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