You’ve probably heard breakfast is the most important meal of the day. Although with the popularity of intermittent fasting, lots of people are skipping their morning meal — especially those trying to lose weight. But, a new study published in the Journal of Clinical Endocrinology & Metabolism might make a convincing case for not just eating breakfast if you want to lose weight, but also eating a big breakfast.
Researchers followed 16 young male participants for two, three-day periods. During one, the men ate a big breakfast (69% of their calories), normal-sized lunch (20% of their calories), and a small dinner (11% of their calories). During the other, they ate a small breakfast, normal-sized lunch, and a big dinner at the same percentages. The total calories for each meal pattern were the same.
The researchers took several measures to ensure more accurate results: Participants stayed in the laboratory during the experiment, and all ate the same food. They also stuck to the same sleep schedule and were told to avoid exercise.
Over the course of each three-day period, the researchers measured the participants’ blood sugar, insulin concentrations and cravings for sweets. They also looked at the rates of diet-induced thermogenesis (DIT) after each meal.
“Diet-induced thermogenesis refers to the amount of energy the body uses to digest food,” explains Amanda Baker Lemein, RD.” In other words, it’s the number of calories your body burns just by digesting food.
The researchers found DIT was generally 2.5 times higher after breakfast than it was after dinner. That may mean if you’re going to consume a higher-calorie meal, you’d be better off doing it in the morning than in the evening.
“It is important to understand that DIT doesn’t have a huge impact on the overall caloric burn — most studies estimate it around 5–15%,” says Baker Lemein. So if your goal is weight loss, simply shifting most of your calories to the early part of the day but keeping the total amount you consume the same may not be enough to help you shed pounds.
But there’s another reason a bigger breakfast may be better than a bigger dinner: The study’s results also showed insulin and blood sugar spikes were not as high with a big breakfast as they were with a big dinner. “It’s understood that insulin sensitivity is higher in the early day hours than in the late evening, which means food eaten earlier is more likely to be utilized as energy as opposed to stored,” explains Liz Wyosnick, RD. “There’s also a lot of evidence that skipping breakfast, or having a low-calorie intake in the first half of the day, may lead to overcompensating in the second half of the day which, regardless of meal timing, can mean more calories taken in than burned, leading to weight gain.”
Interestingly, the researchers also found participants experienced more cravings, particularly for sweets, on the days they ate smaller breakfasts. This seems to support the idea you’re less likely to overeat later in the day if you opt for a big breakfast.
“Bigger doesn’t necessarily mean better if the breakfast contains a lot of processed foods, which are high in added sugars,” points out Kristian Morey, RD. “Also, the thermic effect of food is half of the thermic effect of exercise when it comes to energy expenditure.” In other words, you’re able to burn significantly more calories via exercise than you can by digesting food. “For these reasons, I often find the diet quality [prioritizing whole foods] and an active lifestyle provide the biggest [weight-loss] benefits overall,” says Morey.
It’s worth noting that the sample size of the study is very small (16 healthy young men), Baker Lemein says, which means the findings may not translate directly to the general population. “However, I have found that clients who eat breakfast benefit from weight loss more than those that do not consume breakfast,” she adds.
Ultimately, “it’s worth experimenting with meal sizes and seeing how it affects weight loss for you personally,” says Wyosnick. “I would encourage people to discern if their small breakfast leads to more grazing and snacking in the second half of the day, and therefore inability to stick to their calorie budget. I would also encourage them to reflect on how they feel with a very large dinner.” For example, does it lead to restless sleeping or digestive distress? Those reasons alone might be enough to switch to a smaller dinner, as sleep has a major impact on health, including the ability to lose weight.
As for the benefits of a boost in DIT after a morning meal, Wyosnick says the idea is compelling.
But it’s important to keep the big picture in mind. “For successful weight loss, it always comes back to meeting and not exceeding a calorie goal in a sustainable and consistent manner,” she says. Try logging your meals regularly with an app like MyFitnessPal so you can look at the data and find trends to help meet your goals.