Dear Doctor: I just heard about a new study saying that whole grains can rev up your metabolism and help you lose weight. Do we need to add tons of whole grains to our diets now?
Dear Reader: We think you're referring to a study published in February in the American Journal of Clinical Nutrition. The researchers did reference a connection between eating whole grains and weight loss, but the original purpose of the study was to examine the role that whole grains play in energy balance and in controlling blood sugar. Let's take a closer look.
In the study, 81 men and women ranging in age from 40 to 65 agreed to eat only the food provided to them by the researchers for eight weeks. They didn't change their activity levels and they gave any uneaten food back to the researchers.
For the first two weeks, during which the caloric requirements of each participant were established, everyone ate exactly the same food. For the next six weeks, everyone had basically the same diet, but with one big difference: The food for half of the participants was prepared with whole grains, whereas the others ate foods made with refined grains.
Throughout the study, participants reported on how full or hungry they felt. In addition, measurements were taken for their blood glucose levels, weight and metabolic rate. At the end of the eight-week study, the resting metabolic rates of the individuals eating whole grains were measurably higher than those who were eating refined carbohydrates.
Researchers noted that the group eating whole grains burned 100 more calories per day than did the group eating refined grain products. That's the same as 10 minutes of high-intensity exercise, or a brisk 30-minute walk. Or, alternatively, it's a tablespoon of peanut butter or a medium-sized banana.
So what are whole grains? Oatmeal or whole-wheat bread comes to mind, but grains constitute a large and varied food group. They include barley, corn, amaranth, buckwheat, oats, rye, quinoa, teff, millet, brown rice and wild rice. (Full disclosure -- amaranth, quinoa and buckwheat are considered to be "pseudo grains," but get included because they offer similar nutritional benefits.)
To be considered as "whole," the cereal grain must contain all of its parts -- the germ, the endosperm and the bran. Collectively, they contain important nutrients like soluble and insoluble fiber, B vitamins, minerals like iron, zinc, magnesium and selenium, and micronutrients. Many breakfast cereals and refined products actually start out as whole grains, but during processing are stripped of most of the nutrient-rich and healthful components.
What does this mean for you?
Although whole grains appear to increase metabolic rate, the degree by which they do so is quite modest. That means the results of the study aren't really an excuse to start eating more. What they do reinforce is a dietary principle we have believed to be true for quite some time -- that choosing whole-grain products over refined foods is better for your body and your health.
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