Whether that calorie deficit lasts for more than a few days and leads to weight loss remains to be seen, says Harvard School of Public Health researcher Rania Mekary, PhD. “Your metabolic rate might end up decreasing,” she says. “If you starve yourself, you might lose weight, but is that something good long-term?”
Researchers point out that randomized trials have shortcomings, as well. They are often small and last only a few days.
The bottom line is that while research hasn’t shown eating breakfast can lead to weight loss, neither does it show that eating breakfast makes you pack on the pounds, says Heather Leidy, PhD. She's an assistant professor in the department of nutrition and exercise physiology at the University of Missouri School of Medicine.
Q. What if you don’t eat anything until after you’ve been up for a couple of hours or more? Does that count as breakfast?
A. Does eating later in the morning count as breakfast or a snack, especially if it’s something small and not a calorie-laden meal? In many studies, researchers typically ask only whether participants ate breakfast, not what they ate or when they ate it.
“There’s no real standard definition of breakfast,” says Megan McCrory, PhD. She's an associate professor of nutrition at the Georgia State University Byrdine F. Lewis School of Nursing and Health Professions. Some people might call that container of yogurt scarfed down at their office a morning snack, while others might call it breakfast, McCrory says, muddying the research findings. More study is needed, she said in an article published in July in Physiology & Behavior.
Mekary says she wondered whether people who said they skipped breakfast actually ate the same amount of that meal but called it snacking. She and her colleagues had asked participants in the Nurses Health Study whether they snacked before lunch as well as whether they ate breakfast. In one analysis of their data, Mekary lumped together all of the before-lunch snackers who said they didn’t eat breakfast and compared them to the women who said they did. Both groups had a similarly lower risk of type 2 diabetes compared to women who said they ate nothing before lunch, in part because the morning eaters tended to weigh less. In other words, whether you call it breakfast or a snack and eat it first thing or later in the morning, the potential benefits appear to be similar, Mekary says.