It seems like every 2 years the skeptical cardiologist has to defend skipping breakfast.
I first described how irritating and puzzling I find the concept that skipping breakfast causes obesity and heart disease in a 2013 post entitled “Breakfast is not the most important meal of the day: feel free to skip it.” When I’m irritated with a ridiculous concept I ask lots of questions:
Why would I eat breakfast if I am not hungry in order to lose weight? What constitutes breakfast? Is it the first meal you eat after sleeping? If so, wouldn’t any meal eaten after sleeping qualify even it is eaten in the afternoon? Is eating a donut first thing in the morning really healthier than eating nothing? Why would your first meal be more important than the last? isn’t it the content of what we eat that is important more than the timing?
Most of the studies on the proposed effect of breakfast on obesity (PEBO), I pointed out, are observational studies which cannot prove causality and the few, small prospective randomized studies don’t clearly support the hypothesis.
I suggested that PEBO comes from the breakfast food and cereal industry and should be ignored.
Writing an update on my post in 2015 I referenced Melanie Warner’s excellent book on the methods of the food industry entitled “Pandora’s Lunchbox”
“Walk down a cereal aisle today or go onto a brand’s Web site, and you will quickly learn that breakfast cereal is one of the healthiest ways to start the day, chock full of nutrients and containing minimal fat. “Made with wholesome grains,” says Kellogg’s on its Web site. “Kellogg’s cereals help your family start the morning with energy by delivering a number of vital, take-on-the-day nutrients—nutrients that many of us, especially children, otherwise might miss.” It sounds fantastic. But what you don’t often hear is that most of these “take-on-the-day” nutrients are synthetic versions added to the product, often sprayed on after processing. It’s nearly impossible to find a box of cereal in the supermarket that doesn’t have an alphabet soup of manufactured vitamins and minerals, unless you’re in the natural section, where about half the boxes are fortified.”
The Kellogg’s and General Mills of the world strongly promoted the concept that you shouldn’t skip breakfast because they had developed products that stayed fresh on shelves for incredibly long periods of time. They could be mixed with easily accessible (low-fat, no doubt) milk to create inexpensive, very quickly and easily made, ostensibly healthy breakfasts.
Unfortunately, the processing required to make these cereals last forever involved removing the healthy components.
As Warner writes about W.K. Kellogg:
“In 1905, he changed the Corn Flakes recipe in a critical way, eliminating the problematic corn germ, as well as the bran. He used only the starchy center, what he referred to as “the sweetheart of the corn,” personified on boxes by a farm girl clutching a freshly picked sheaf. This served to lengthen significantly the amount of time Corn Flakes could sit in warehouses or on grocers’ shelves but compromised the vitamins housed in the germ and the fiber residing in the bran”
In 2017 I felt compelled to revisit the topic when a New York Times piece made the case for making breakfast a feast:
The writer, Roni Rabin (who has a degree in journalism from Columbia University) struggles to support her sense that there is a “growing body of research” suggesting we should all modify our current dietary habits in order to eat a breakfast and make breakfast the largest meal of the day
My post entitled “Ignore The New York Times and The American Heart Association and Feel Free to Skip Breakfast” examined the weak evidence for benefits of “mindful” eating and harms of skipping breakfast.
A new study has popped up and, of course, been widely publicized as supporting eating breakfast. Fortunately, it caught the eye of Peter Attia thus saving me from having to read the article.
Below are some of his scathing comments, taken from one of his non-lame weekly emails:
You’ve probably heard that breakfast is the most important meal of the day. “What is less commonly mentioned,” writes Alex Mayyasi in The Atlantic, “is the origin of this ode to breakfast: a 1944 marketing campaign launched by General Foods, the manufacturer of Grape Nuts, to sell more cereal.”
Seventy-five years later, here’s the latest report from the April issue of the Journal of the American College of Cardiology: “Taken together, these studies [showing a positive association between skipping breakfast and CVD and CVD risk factors] as well as our findings underscore the importance of eating breakfast as a simple way to promote cardiovascular health and prevent cardiovascular morbidity and mortality.”
What were the findings? Let’s look at a few newspapers:
- “Want to Lower Your Risk for Heart Disease? Eat Breakfast Every Morning” (Healthline)
- “Eating breakfast? Skipping a morning meal has higher risk of heart-related death, study says” (USA TODAY)
- “Study: Skipping breakfast increases risk of heart disease mortality by 87 percent (FOX)”
(You may notice that all three headlines imply causality.)
Looks like General Foods was right. Time to reach for the Lucky Charms? Perhaps it’s time to put on our critical thinking cap instead. The actual study, and the media coverage of it, is a part of the Groundhog Day that is observational epidemiology (for more on the limitations of this type of research, check out Studying Studies: Part II). This was a prospective cohort study pulling data from NHANES III, looking at people who reportedly eat breakfast every day to people who never eat breakfast, and then following up with them (about 19 years later on average), tallying up the deaths from CVD and deaths from all causes.
One question to ask about the population studied is: was eating breakfast or not eating breakfast the only difference between these two groups? In other words, were there any confounding factors (for more on confounding, see Studying Studies: Part IV)? The authors reported that, “participants who never consumed breakfast were more likely to be non-Hispanic black, former smokers, heavy drinkers, unmarried, physically inactive, and with less family income, lower total energy intake, and poorer dietary quality, when compared with those who regularly ate breakfast.” Not only that, “participants who never consumed breakfast were more likely to have obesity, and higher total blood cholesterol level than those who consumed breakfast regularly.” They also had a higher reported incidence of diabetes and dyslipidemia. Read that again, please.
While the study used statistical models to “adjust for” many of these potential confounders, it’s extremely difficult (actually, it’s impossible) to accurately and appropriately adjust for what amounts to fundamentally different people. The healthy user bias (or the inverse, an unhealthy user bias) is virtually impossible to tease out of these studies (the healthy user bias is covered in more depth in Studying Studies: Part I). Not only that, you never really know what you’re not looking for. This is typically referred to as residual confounding in the literature, where other factors may be playing a role that go unmeasured by the investigators.
I haven’t even yet mentioned the misleading nature of reporting relative risk — in this case, an associated 87% (reported in the study as a hazard ratio of 1.87) — without reporting absolute risk. The question you should always ask is, 87% greater than what? To get an idea of the associated absolute risk, the number of CVD deaths in the “every day” breakfast group were 415 out of a total of 3,862 people over 16.7 years (that’s an unadjusted rate of 10.7%) while the numbers for the “never” breakfast folks were 41 CVD deaths out of a total of 336 people over 16.7 years (unadjusted rate of 12.2%). That’s an absolute difference of 1.5% over almost 17 years (annually, this is an absolute difference of 0.09%). Granted, this is before adjustment of the myriad confounders (including the biggest “risk factor” for CVD death, age, in which the “never” breakfast group was younger on average at baseline), but it gives you an idea that we’re looking at small differences even over the course of a couple of decades. This looks a lot difference on paper than an associated 87% increased risk of CVD death. (For more on absolute risk and relative risk, see Studying Studies: Part I.)
- What were the participants actually eating for breakfast? We don’t know. The investigators didn’t have information about what foods and beverages they consumed.
- Did participants change their breakfast eating (or abstaining) habits over the course of almost 20 years? We don’t know. Information on breakfast eating was only collected at baseline.
- Could there be errors in the classification of the causes of death in the participants? It’s possible.
- What constitutes skipping breakfast? Was it the timing of the first meal of the day? We don’t know. Participants were asked, “How often do you eat breakfast?” but there was no definition of what that means, exactly.
What’s more likely: reported skipping breakfast was a marker for a lifestyle and environment that may have predisposed these people to a higher risk of CVD death or that skipping breakfast itself causes CVD death?
Go ahead and skip all the breakfasts you want. And please forward this to the next 10 people who tell you it’s unhealthy to do so.
And ditto for this post.