You might have heard that interval training, standing desks and sunshine boost metabolism, but whole grains?
New research from Tufts University published in the American Journal of Clinical Nutrition suggests that substituting whole grains for refined grains speeds up metabolism and increases calorie loss by reducing calories retained during digestion.
Previous epidemiology studies have suggested that whole grains and high fiber are good for glycemic control and insulin sensitivity. But there’s been controversy over whether they’re beneficial for weight loss, according to a Tufts release about the research.
The new eight-week, randomized, single-blind comparative study included 81 men and women between the ages of 40 and 65. All participants ate the same type of food in the first two weeks, and the researchers determined their individual calorie needs. After two weeks, they randomly assigned subjects to eat a diet that included either whole grains or refined grains. The whole-grain diet and the refined-grain diet differed mostly in grain and fiber content—the energy, macronutrient composition, type of food and meal structure were similar.
Throughout the eight weeks, researchers measured weight, metabolic rate, blood glucose, fecal calories, hunger and fullness. At the end of the study, those who ate whole grains had an increase in resting metabolic rate and fecal energy losses compared to those who ate refined grains. The extra fecal energy losses were not due to the extra fiber itself (which was accounted for in calculations) but from the effect the fiber had on the digestibility of other food calories.
The people who ate a diet with whole grains that matched the recommended dietary allowance for fiber lost close to an extra 100 calories per day. This was due to a combination of an increased resting metabolic rate and greater fecal losses.
“We provided all food to ensure that the composition of the diets differed only in grain source,” the study’s senior author, Susan B. Roberts, PhD, senior scientist and director of the Energy Metabolism Laboratory at USDA HNRCA, said in the release. “The extra calories lost by those who ate whole grains was equivalent of a brisk 30-minute walk—or enjoying an extra small cookie every day in terms of its impact.”
This is good news for all the people who say they’re eating more whole grains. A recent Truven Health Analytics-NPY Health Poll found that 27 percent of people say they’re eating more whole grains than they did six months ago.