Metabolism is a finicky chemical process that can be influenced by anything from your workout routine to how much water you drink in a day. For that reason, much research has been devoted to discovering which foods can speed up or slow down your metabolism in an effort to manipulate weight and energy levels.
Case in point: a new study published last week in The American Journal of Clinical Nutrition that found that substituting refined grains with whole grains aids in the absorption of fiber, which boosts metabolism and regulates weight. Whole rye, oats, quinoa, barley, millet, buckwheat, brown rice, and spelt are all examples of healthy whole grains.
To arrive at this conclusion, the researchers fed 81 participants two different diets over an eight-week period: one with refined grains and one with whole grains. People who ate the latter diet lost an extra 100 calories per day "due to a combination of increased resting metabolic rate and greater fecal losses," writes Tufts University of the results.
"We provided all food to ensure that the composition of the diets differed only in grain source," said study author Susan Roberts, Ph.D. and senior scientist and director of the Energy Metabolism Laboratory at Tufts. "The extra calories lost by those who ate whole grains was equivalent [to] a brisk 30-minute walk—or enjoying an extra small cookie every day in terms of its impact."
It's worth mentioning that this research was supported by the General Mills Bell Institute of Health and Nutrition as well as the U.S. Department of Agriculture. With that said, the idea that whole grains are healthier than refined is widely supported in the health and wellness fields—even the Dietary Guidelines for Americans recommend we fill up on whole grains and limit refined.
For more on metabolic health, read up on healthy ways to boost metabolism (without going to the gym).