For years, nutrition experts have been describing the health benefits of avoiding refined grains in your diet and eating more whole grains. But a new study definitively shows the weight-related benefit of whole-grain consumption.
You may already know that whole grains have more dietary fiber, and nutrients such as iron, potassium, magnesium, calcium, B vitamins and vitamin E. They not only help you feel full longer, they are also associated with reducing disease and mortality. Heart attack and cardiovascular disease, cancer and type 2 diabetes are all reduced in people who eat more whole grains.
A study published this past June in the AHA journal Circulation, reported eating 48 grams or more every day translated to a 20% lower risk of death from all causes and a 25% lower risk of dying from cardiovascular disease.
And a new meta-analysis of published studies and data from 786,076 men and women showed that for about every serving (16 grams) of whole grains there was a:
- 7% lower risk of total deaths
- 9% lower risk of cardiovascular disease-related deaths
- 5% lower risk of cancer-related deaths
The more whole grains consumed, the lower the death rate. When three servings (48 grams) were consumed daily the risks were lower by:
- 20% for total deaths
- 25% for cardiovascular deaths
- 14% for cancer-related deaths
And as servings increase, the benefits continue to increase.
This is where it gets really interesting. In a new peer-reviewed randomized controlled-feeding study, co-authored by iDiet’s Dr. Susan Roberts of Tufts University and published online this month in the gold standard of nutrition journals, The American Journal of Clinical Nutrition, researchers concluded that swapping whole grains for refined flour correlates with an increase in calorie loss because it reduces the amount of calories that are retained during digestion, and appears to boost metabolism by about 100 calories a day or 700 calories a week. The whole-grain eaters also showed modest improvements in healthy gut microbes and immune system T-cell response.
Researchers at Tufts University’s Energy Metabolism Laboratory, which is directed by Dr. Roberts, recruited 81 adults (men and women aged between 40 and 65) and divided them between two separate diets, identical in calories and foods except for grain type. The plan was to see how each diet impacted resting metabolic rate (how the body burns calories when sedentary) and calorie loss (the number of calories burned during digestion itself). Both of these factors can influence your weight. For the first two weeks, both groups ate the exact same foods, and then were divided into either a whole-grains group or a refined-grains group for the next six weeks. All food was provided by the researchers to prevent cheating or accidental variation.
By the end of the study period, the metabolic rate of those fed whole grains had increased while that of the refined-grains group had not. The participants on the whole-grains diet also lost more calories through their poop — and those calories weren’t just from undigested fiber. The researchers subtracted the fiber calories out of the analyses, so the extra caloric loss reflected fiber’s positive impact on excretion of other calories in the diet.
We spoke with lead study author Dr. Susan B. Roberts, senior scientist at the USDA Nutrition Center at Tufts and founder of the iDiet weight management program. She says “the study shows that fiber doesn’t just keep you full but it also increases your metabolism and helps eliminate additional calories through reducing the efficiency of absorption.”
She explained the reason whole grains increase resting metabolism and calorie loss is likely tied to two factors: “The fiber in whole grains might increase metabolic rate by smoothing out the metabolic fuel availability in the body. Additionally, the higher-fiber foods may prevent some of the fat in the diet from being absorbed into the bloodstream.”
Dr. Roberts says these effects can absolutely help you shed pounds over time. “The bottom line of weight loss is calories in versus calories out, but in the real world, you need to be savvy about how you accomplish that.” she says. “That doesn’t mean you can eat anything you want as long as you count calories. Rather, you want to choose high-fiber foods that’ll fill you up, prevent hunger, and increase the number of calories that go out. This can tip the scale in a beneficial way. The extra calories lost by those who ate whole grains was equivalent of a brisk 30 minutes walk – or a cookie every day in terms of its impact.”
Unlike the laboratory-specific or highly specialized diets used in many studies, which you couldn’t feasibly follow in real life, this particular whole-grains diet was very realistic. “We used grocery-store cereals and breads to add whole grains and fiber and to replace more-refined products like white bread,” says Dr. Roberts. “It would be totally easy to replicate this diet, and there’s no reason why you wouldn’t get these same benefits. This is a very practical way to help with weight management.”
In fact, the foods used in this study were so common that you could actually do better yourself, by either eliminating all refined products, or by following a plan like the iDiet provides. The iDiet meals provide more fiber than the relatively low current USDA guidelines used in this study. Our bodies can easily handle more fiber than the USDA guidelines, so the iDiet is designed with more fiber as well as higher protein and lower glycemic load, to not only control hunger but also maximize fat loss at the maximum healthy rate of about 1% of bodyweight per week.
Ref: Am J Clin Nutr ajcn139683
First published February 8, 2017, doi: 10.3945/ajcn.116.139683