Breakthroughs in the field of chronobiology—the study of our circadian rhythms—help solve the mystery of the missing morning calories in breakfast studies.

Where did this whole “breakfast is the most important meal of the day” concept come from? “The Father of Public Relations,” Edward Bernays, infamous for his “Torches of Freedom” campaign to get women to start smoking back in the 1920s, was paid by a bacon company to popularize the emblematic bacon-and-eggs breakfast. The role of public relations, he wrote in his book Propaganda, is the “conscious and intelligent manipulation of the organized habits and opinions of the masses….” Public relations specialists thereby “constitute an invisible government, which is the true ruling power of our country….”

Breakfast is big business. Powerful corporate interests, such as the cereal lobby, are blamed for “perpetuating myths such as the value of consuming breakfast.” An editorial in The American Journal of Clinical Nutrition urged nutrition scientists to speak truth to power and challenge conventional wisdom when necessary “even when it looks like we are taking away motherhood and apple pie.” “Actually,” the editorial concludes, “reducing the portion size of apple pie might not be a bad idea, either.”

So, should we “break the feast” and skip breakfast to lose weight? As I discuss in my video Is Skipping Breakfast Better for Weight Loss?, though “the advice to eliminate breakfast will surely pit…nutritional scientists…against the very strong and powerful food industry,” skipping breakfast has been described as “a straightforward and feasible strategy to reduce total daily energy [caloric] intake.” Unfortunately, it doesn’t seem to work.

Most randomized controlled studies of breakfast skipping found no weight-loss benefit to omitting breakfast. How is that possible if skipping breakfast means skipping calories? The Bath Breakfast Project, a famous series of experiments run not out of a tub, but the University of Bath in the UK, discovered a key to the mystery. Men and women were randomized to either eat breakfast (defined as taking in at least 700 calories before 11:00 am) or fast until noon every day. As you can see in the graph below and at 2:15 in my video, as in other similar trials, the breakfast-eating group ate a little less throughout the rest of the day but still ended up with hundreds of excess daily calories over the breakfast skippers.

Those who ate breakfast consumed more than 500 more calories a day. Over six weeks, that would add up to more than 20,000 extra calories. Yet, after six weeks, both groups ended up with the same change in body fat, as you can see below and at 2:36 in my video. How could tens of thousands of calories just effectively disappear? 

If more calories were going in with no change in weight, then there must have been more calories going out. And, indeed, as you can see in the graph below at 2:52 and in my video, the breakfast group was found to spontaneously engage in more light-intensity physical activity in the mornings than the breakfast-skipping group. Light-intensity activities include things like casual walking or light housecleaning, not structured exercise per se, but apparently, enough extra activity to use up the bulk of those excess breakfast calories. There’s a popular misconception that our body goes into energy conservation mode when we skip breakfast by slowing our metabolic rate. However, that does not appear to be true. But, maybe our body does intuitively slow us down in other ways. When we skip breakfast, our bodies just don’t seem to want to move around as much. 

The extra activity didn’t completely make up for the added calories consumed by the breakfast group, though. We seem to still be missing about a hundred daily calories, suggesting there may be another factor to account for the mystery of the MIA morning calories. Recent breakthroughs in the field of chronobiology—the study of our body’s natural rhythms—have unsettled an even more sacred cow of nutrition dogma: the concept that a calorie is a calorie. It’s not just what we eat, but when we eat. Same number of calories, different weight loss, depending on meal timing.  

Just to give you a taste: As you can see in the graph below and at 4:11 in my video, the exact same number of calories at breakfast are significantly less fattening than the same number of calories eaten at supper. Mind-blowing!

A diet with a bigger breakfast causes more weight loss than the same diet with a bigger dinner, as shown below and at 4:23 in my video. Because of our circadian rhythms, morning calories don’t appear to count as much as evening calories. So, maybe breakfast should be the most important meal of the day after all. 

If you missed my last video, catch up with Flashback Friday: Is Breakfast the Most Important Meal for Weight Loss or Should It Be Skipped?

Did I pique your interest in chronobiology? If so, you’re in luck. See more in the related posts below. 

For some breakfast inspiration, check out A Better Breakfast and my recipe videos for a vegetable smoothie and a grain bowl from The How Not to Die Cookbook


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