Skipping Breakfast & Eating Dinner Late May Decrease Calorie Burn, a New Study Suggests
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Whether the goal is improving heart health, living longer, keeping your brain sharp, losing weight or boosting energy, Americans tend to focus a lot on what to eat. (And what not to. As a quick reminder, here at EatingWell we are firm believers there's room for any food or drink—that you're not allergic to—as part of an overall healthy diet!)
Our dietitians totally understand and support keeping an eye on what's on your plate, of course. In tandem with our genetics, our daily choices, noshes and movement patterns add up to make a big difference in our overall well-being. Still, we're learning more about how it's not just about overall diet quality; quantity (ICYMI, here's how much protein you really need to eat) and timing appear to matter, too.
Skipping breakfast and eating a late dinner tends to increase hunger levels and decrease daily average calorie burn, according to a small study published October 4, 2022, in the journal Cell Metabolism. Read on for the dish, and more details about the meal-timing strategy that might be best for those seeking weight loss or maintenance.
Related: Why It's Actually Rude to Compliment Someone's Weight Loss, According to a Dietitian
What This Diet Study Found
After noticing that previous studies had shown a link between higher weight and increased body fat among those who eat more of their calories later in the day, scientists designed this study to try to learn more about why this might occur.
First author Nina Vujovic, Ph.D., a researcher in the Medical Chronobiology Program in the Brigham and Women's Hospital Division of Sleep and Circadian Disorders in Boston, tells Brigham and Women's Hospital Newsroom: "In this study, we asked, 'Does the time that we eat matter when everything else is kept consistent?'"
To try to answer that question, the team tapped 16 adults (5 women and 11 men) with an average body mass index (BMI) of 28.7. Before spending time in a lab, each participant followed a fixed sleep and wake cycle for 2 to 3 weeks, and they followed a timed and prepared diet during the final 3 days leading up to the official start.
The participants then entered a lab environment (so the researchers could try to control as many variables as possible) and were then separated into one of two groups:
Eat breakfast at 8 a.m., lunch at 12 p.m. and dinner at 5 p.m.
Eat meal one at 12 p.m., meal two at 5 p.m. and meal three at 9 p.m.
After following one eating-timing style, there was a buffer period of 3 to 12 weeks, then the groups swapped meal timings. Regardless of meal timing, all participants were instructed to sleep from midnight until 8 a.m.
During the study, each individual regularly documented their appetite levels. They also had their body temperature checked, energy expenditure monitored and blood samples taken throughout the day. To track how eating time might impact how the body stores fat, the scientists also took biopsies of fat tissue from a subgroup of the participants in both test groups so they could compare the gene expression patterns between the two.
Eating later—the noon-to-9 p.m. style—had "profound effects" on two hormones that play a role in our appetite, hunger levels and overall drive to eat: leptin and ghrelin. Leptin tells our brain that we're satisfied, and levels of this hormone decreased among those in the later-eating group compared to their 8 a.m. meal-starting peers. Later eaters also burned calories at a slower rate and appeared to have gene expressions related to increased fat storage.
Related: These Are the Worst Foods to Have Before Going to Bed
Since this was a randomized study that had a "crossover" format, meaning each individual participated in both test groups, and because this was all performed in a lab that controlled for external factors like sleep, physical activity, light levels and beyond, the scientists stand by their results.
"We found that eating four hours later makes a significant difference for our hunger levels, the way we burn calories after we eat and the way we store fat," Vujovic adds in the news release.
Still, 16 people (less than a third of whom were women) is a very small sample of the entire population. That said, the researchers designed the study this way so they could keep close track of each participant, have them stay in the lab and control all of those other elements.
"We isolated these effects by controlling for confounding variables like caloric intake, physical activity, sleep and light exposure, but in real life, many of these factors may themselves be influenced by meal timing," Frank A.J.L. Scheer, Ph.D., the director of the Medical Chronobiology Program, tells Brigham and Women's Hospital Newsroom. "In larger scale studies, where tight control of all these factors is not feasible, we must at least consider how other behavioral and environmental variables alter these biological pathways underlying obesity risk. "
In the future, the scientists affirm that they hope to continue diving into this topic while tapping a larger and more diverse population.
Related: The #1 Food You Should Eat for Breakfast
The Bottom Line
A new diet study found that skipping breakfast and eating a late dinner around 9 p.m. may significantly impact our appetite, energy expenditure and how we store fat (as well as how much fat we store).
Since this was a fairly small study, and only one of many in the field of meal timing, much more research is needed to confirm these connections.
It does align with our earlier guidance about the best times to eat for weight loss, however, and is a nice reminder that skipping meals is not a smart strategy. In case you could use some extra inspiration about the "what" now that you know more about the "when," check out our guide to the 10 best healthy breakfast foods, how to prep a well-balanced lunch and 20 good-for-you dinners you can make in 20 minutes or less.
