Is breakfast really so important? Understanding correlation and causation

Shireen Partovi
5 June 2017

Above: Image © DimensionsDesigns , iStockphoto.com

“Breakfast is the most important meal of the day.” How often have you heard that from your parents, your teachers, your doctor...? You may have even said it yourself!

People have been talking about the importance of breakfast for decades. But in recent years, scientists have begun to question this popular claim. Is it really a scientific fact?

Spoiler alert: the answer’s not as simple as you might think! There are a lot of studies that talk about the health benefits of breakfast. But some of them require a closer look. Although these studies may find a connection between breakfast and good health, that doesn’t necessarily mean that breakfast causes good health.

What do the studies say?

One scientific study says that eating breakfast helps improve concentration, memory and attention. Another says that eating breakfast is associated with low blood pressure. Others say that skipping breakfast can lead to type 2 diabetes, cardiovascular disease and other health concerns. Yet another says that eating high-protein breakfasts makes you less likely to eat foods rich in sugar and fat later in the day, and that skipping breakfast is strongly associated with obesity.

After all that, you might assume that the argument has been settled: breakfast has magical properties and will turn anyone who eats it into the picture of perfect health. But scientists who have looked more closely at some of these studies sometimes have different opinions. Let’s look at the studies on breakfast and weight gain to see why.

Did you know? Breakfast did not become a normal part of everyday life until around the 1600s. In fact, eating breakfast used to be seen as gluttonous, and people actually frowned on it!

The fine print

Many of the studies linking breakfast and weight gain are observational. Observational studies show correlation, but usually not causation. In other words, these studies showed an association between skipping breakfast and weight gain. However, they did not provide clear evidence that skipping breakfast actually caused weight gain.

Observational studies are useful for scientific discovery. And they can sometimes help identify a causal relationship. But it’s important to recognize the difference between correlation and causation. It’s one reason why the jury is out on the topic of breakfast and obesity.

There are other reasons, too. An article in The American Journal of Clinical Nutrition reviewed a number of studies on the link between skipping breakfast and weight gain. The article says that many of these studies cited previous work improperly. They also used misleading and biased language to push the idea that eating breakfast directly leads to weight loss.

Meanwhile, another study found no difference in weight loss for people who ate breakfast and those who skipped it. Obviously, this contradicts the findings of other breakfast studies.

Did you know? Queen Elizabeth I of England was a big fan of breakfast, which helped the meal gain popularity throughout Europe.

What’s the takeaway?

So does breakfast have magical powers? The answer is still up in the air. Of course, you shouldn’t ignore the fact that eating breakfast has benefits. But keeping you from gaining weight isn’t necessarily one of them. And skipping breakfast will not necessarily make you obese.

This topic shows why it’s important to critically analyze everything that you read. That’s a key skill for every scientist—and every citizen—to have!

Shireen Partovi