Whole grains have been shown to be superior in the diet when compared with refined grains, suggests new research published in the American Journal of Clinical Nutrition. Whole grains increased calorie loss by decreasing the number of calories retained during digestion, while simultaneously speeding up metabolism.
In the new research, investigators conducted a study over 8 weeks that included 81 men and women aged between 40 and 65. All food was provided to the participants over the course of the study and included either whole grains or refined grains. Participants were asked only to consume the food provided, return any uneaten food, and continue with their usual levels of physical activity.
“We provided all food to ensure that the composition of the diets differed only in grain source,” says senior author Susan B Roberts, Ph.D., senior scientist and director of the Energy Metabolism Laboratory at the USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University in Boston.
For the first two weeks, all participants ate the same type of food, and the calorie needs of each individual were determined. The participants were then randomly assigned to either a group that included whole grains or a group with refined grains. They provided stool samples, gave blood samples, and had their metabolic rate tested. The researchers compared the effects of whole grains and refined grains on resting metabolic rate and faecal energy losses, in addition to how full or how hungry the participants felt. Measures of the study included weight, metabolic rate, blood glucose, faecal calories, hunger, and fullness.
Results showed that the group that ate whole grains had increased resting metabolic rate and greater faecal losses compared with the refined grain group. Participants who consumed whole grains – an amount that matched the recommended daily allowance for fibre – lost almost an extra 100 calories per day than the participants who consumed refined grains without much fibre.
Many previous studies have suggested health benefits of whole grains and high dietary fibre intake, including for glycaemic control and insulin sensitivity. There has been controversy, however, about whether whole grains and fibre are beneficial for weight regulation, partially because there hasn’t been data from controlled metabolic studies.
The latest study was carried out by researchers from Tufts University, the University of Minnesota, and the Bell Institute of Health and Nutrition, in the US.