Switching to whole-grain foods might help keep your weight in check as much as a brisk 30-minute daily walk would, a new study suggests.
Volle granen lijken zowel het aantal calorieën dat je lichaam opneemt tijdens de spijsvertering te verlagen als de stofwisseling te versnellen, legt studieauteur J. Philip Karl uit. Hij is een voedingswetenschapper die het onderzoek deed terwijl hij promoveerde. student voeding aan de Tufts University in Boston.
Hoewel uit andere onderzoeken is gebleken dat mensen die volle granen eten slanker zijn en minder lichaamsvet hebben dan degenen die dat niet doen, zei Karl dat het moeilijk is om de effecten van volle granen te scheiden van regelmatige lichaamsbeweging en een gezonder dieet in het algemeen. Dus voor de nieuwe studie “controleerden we het dieet strikt. We lieten ze niet afvallen”, zei hij. De onderzoekers deden dat door de specifieke caloriebehoeften van elk van de 81 mannen en vrouwen in de leeftijd van 40 tot 65 jaar in het onderzoek in kaart te brengen.
For the first two weeks of the study, everyone ate the same types of food and the researchers computed their individual calorie needs to maintain their weights. After that, the researchers randomly assigned people to eat either a whole-grain or refined-grain diet.
The men and women were told to eat only the food provided and to continue their usual physical activity.
Those on the whole-grain diet absorbed fewer calories and had greater fecal output. Their resting metabolic rate (calories burned at rest) was also higher. The fiber content of whole-grain foods, about twice that of refined-grain foods, is believed to play a major role in those results, Karl said.
“The energy deficit in those eating whole grains compared to refined grains would be equivalent to the calories you would burn if you were to walk about a mile [in] about 20 or 30 minutes,” he said. But the study did not prove that whole grains cause weight loss. ”We don’t know over the long term if it would translate to weight loss,” Karl said, but his team suspects it would. “This would translate to about 5 pounds in a year,” Karl estimated.
The study is solid, said Connie Diekman, director of university nutrition at Washington University in St. Louis.
“It provides good evidence that consumption of whole grains is an important part of a healthful eating plan,” Diekman said. The study documents how whole grains contribute to feelings of fullness and appear to increase metabolism, she added. “The study was short in duration and somewhat limited in population diversity, but the outcome is a positive nutrition recommendation that anyone could benefit from,” she said.
The study was published online Feb. 8 in the American Journal of Clinical Nutrition.
In a related study in the same issue of the journal, the same group of researchers found that people who ate whole grains had modest improvements in healthy gut environment and certain immune responses. Whole-grain intake has also been linked with a reduced risk of heart disease, type 2 diabetes and some cancers, the researchers noted.
Inhoud
How do you find whole-grain products?
Look on the label for ”100 percent whole grains,” Karl said. “Just because something is made with whole grains doesn’t mean there has to be much in there,” he explained. “Look to see if the first ingredient is whole grain, and 100 percent.”
There may also be a label, issued by the Whole Grains Council, that indicates what percent of whole grain a food contains, he added.
Karl is now a nutrition scientist with the U.S. Army Research Institute of Environmental Medicine.
The current Dietary Guidelines for Americans recommend eating six servings of grains daily, with at least half of those servings being whole grains.
