What did you eat for breakfast today? If it was oatmeal, you might find yourself feeling fuller longer and even eating less at lunch, according to a new study published in the journal Annals of Nutrition and Metabolism.
In the latest science-backed battle of the breakfast foods, researchers from the New York Nutrition Obesity Research Center at St. Luke’s Hospital in New York City tested whether a breakfast of corn flakes or oatmeal would help people feel more satiated.
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Your Body on Oatmeal
For their small study, researchers recruited 36 participants, half of them were at a normal weight while the other half were overweight. On different days, the participants consumed one of three different breakfasts — oatmeal, sugar-sweetened cornflakes or just water. Each person also underwent blood tests measuring for glucose, insulin and to trace how quickly food left their stomach after eating.
“We tried to make [the breakfasts] as similar as possible by adding a certain amount of milk to the corn flakes, but they weren’t exactly the same,” says study author Allan Geliebter, PhD, research psychologist in the Department of Psychiatry at Mount Sinai St. Luke’s Hospital. “The total calories were the same, but the oatmeal has eight grams of fiber, whereas the corn flakes have zero.”
We all know that if your breakfast doesn’t keep you full until lunch, it’s fairly worthless (right?). So within three hours of eating breakfast, participants were fed a nutritious liquid lunch through a straw from a concealed container (so that seeing how much they’d consumed wouldn’t influence how much they finished). That’s when Geliebter says things got surprising. Normal weight participants consumed 30 percent less for lunch when they’d eaten oatmeal for breakfast, compared to cornflakes. But overweight participants ate 50 percent less for lunch after eating oatmeal, as opposed to the cereal.
Even more interesting was that both breakfasts had nearly the same glycemic index levels, a measure of how much a carbohydrate will raise your blood sugar levels. “People talk about glycemic index as promoting fullness, so something that has a low glycemic index should make you feel fuller,” Geliebter says. Yet, fiber appears to have trumped the GI index in terms of improving satiety here.
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Fiber: Oatmeal’s Star Nutrient
One reason fiber is so important: It may cause food to linger in your stomach longer. Researchers tested how long it took oatmeal to digest compared to corn flakes or water using a tracer mixed in with each meal. Oatmeal stuck around the longest. “We think the emptying of the food from the stomach is related to fiber. It takes a longer time to leave the stomach and holds on to fluid more,” Geliebter says.
Blood tests also showed that the sugar in the cornflakes might have also made a difference in hunger levels. “We measured blood sugar before and for about 180 minutes after the meal… For the sugared corn flakes, the blood sugar started falling near the end of the [three hour] period and coincided with increased hunger.”
Yet, the researchers aren’t entirely sure why overweight people saw a greater effect compared to normal weight participants. “I could speculate that [it’s known that] overweight people tend to consume less fiber, so eating oatmeal the fiber effect may have been greater because they weren’t used to it.”
While Geliebter notes that this study alone is too small to indicate that oatmeal can lead to weight loss, he says that the results are intriguing. “Oatmeal, which has a lot of fiber in it, seems to make people feel fuller and leads to them eating a smaller lunch, [which might mean] they’re consuming fewer calories,” he says.