Why Are Scientists So Sure Breakfast Helps You Lose Weight?

Health and medicine explained.
Sept. 9 2013 1:20 PM

Cuckoo for Cocoa Puffs

Why are we so sure that breakfast is the most important meal of the day?

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What accounts for this redundancy? It’s mostly to do with cost, says Mark Pereira, a University of Minnesota researcher who published the most recent association study on breakfast and obesity in June. At this point such research may not advance the state of knowledge very far, but it’s cheap to do. By drawing on an existing data set—the Framingham Heart Study, for example, or CARDIA—a scholar can finish an analysis for a few thousand dollars. Pereira would like to follow up his work with a randomized experiment in which subjects are assigned to breakfast and no-breakfast groups, then followed for two months. That would give a better sense of whether breakfast really prevents weight gain, but Pereira would need a $2 million or $3 million grant to make it happen and several years of research time.

Meanwhile, the National Institutes of Health may be unwilling to invest that much money when the value of a healthy breakfast has already been established as a principle of common sense. We’ve had so many association studies now, completed in different contexts but arriving at the same results, that funding agencies may assume the question has already been decided.

The redundant work could hurt breakfast science in other ways as well. Every time a research group suggests that eating breakfast might prevent weight gain, more health-conscious people make a point of doing so. This could exacerbate the confounds that we knew about already: Now the healthiest, thinnest people in the population will be even less likely to skip their morning meals than they were before—and the putative “effect” of eating breakfast will seem to grow in size.

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This self-fulfilling prophecy may bewilder even scientists. Brown and his colleagues showed that many scholars of nutrition are already in the tank for breakfast. They checked the abstracts of papers on breakfast and obesity to see if the associations between breakfast and obesity were being misconstrued as something more. At least one-fourth of all the studies in their database made “unqualified causal claims” about their data, they said, and improperly declared that skipping breakfast actually causes obesity. Another 25 percent hinted at a causal relationship with weasel phrases like “breakfast habits may contribute to obesity” or “the data suggest that it does.”

The pro-breakfast bias seemed even more egregious when Brown et al. looked at how these papers cite existing literature. In referring to a randomized trial from 1992—one of very few such experiments on the relationship between eating breakfast and gaining weight—more than half exaggerated its findings to make breakfast sound important. According to that study, people who normally skip breakfast did lose more weight when they were told to change their morning routine. But the opposite was true for habitual breakfast-eaters, who lost more weight when they stopped eating breakfast.

Why should anyone try to thumb the scale for eating breakfast? Are these scientists taking money from Big Granola? For other tricky issues in nutrition—such as whether drinking diet soda makes you fat, or whether breast-feeding keeps your children thin—it’s hard to keep the science free of interest groups and ideology. When it comes to eating breakfast, though, there shouldn’t be much controversy. Bias on this issue wouldn’t seem to be inspired by the private sector or egged on by politicians. Instead, it could have developed naturally, from the overconfidence of scientists. “There’s a lot of scientific dogma in the field that has nothing to do with industry,” says Pereira. “People just want to be ‘right.’ It’s really, really a mess.”

Still, it might not be such a good idea to wait around for better evidence. Advising people to eat breakfast may not really help to keep you thin, but there isn’t any evidence that it makes you fat. It’s also possible (but by no means certain) that breakfast improves cognitive abilities and mood in kids and teenagers. So what’s the harm in trying, just in case it works?

There may be a downside to the breakfast bias, though, if it contributes to a din of pointless health advice. When Dr. Oz and the surgeon general remind us to eat breakfast, they’re adding to a growing list of do’s and don’ts that are getting hard to keep track of. “People can only hold on to so many nutritional rules at one time,” says Brown. “We have to ask, is there something more important that they could have communicated instead?”

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