This was a 6-week randomized, single-blind, parallel-arm controlled- feeding study. All the food and drinks were provided throughout the study. In fact, the participants were asked to eat breakfast at the research center 3x/week.
The study included 49 men and 32 women (ages 40-65 with Body Mass Index < 35). The participants were assigned to one of two diets. The first was a whole grains diet with roughly 207 grams of whole grains plus 40 grams of dietary fiber per day. The second was a refined grains diet with 0 grams of whole grains and 21 grams of fiber per day.
Adherence to the whole grain diet was measured by checking plasma levels of alkylresocrinol. These are phenolic lipids found mainly in bran fractions of wheat, rye, barley, and triticale. Thus, alkylresocrinol concentration can be thought of as a biomarker for whole-grain intake.
The authors also collected stool produced over 72 hours at the start and end of the study. After freeze-drying, their heat of combustion was measured using an Isoperibol Bomb Calorimeter.
Lastly, the resting metabolic rate was also measured at both the start and end of the study. The final calculation was done using Weir’s equation (REE = [3.9 (VO2) + 1.1 (VCO2)] 1.44).
- Resting Metabolic Rate was higher by 43 kcal/day for the whole grains group than for refined grains.
- The stool weight increased by 76 grams/day for the whole grains group than for refined grains.
- The stool energy was 57 kcal/day higher in the whole grains group than in the refined grains group.
- The combined effects of the above findings showed the whole grain group to have a 92 kcal/day increased energy loss compared to refined grains.
Karl JP, Meydani M, Barnett JB, Vanegas SM, Goldin B, Kane A, … Roberts S. Substituting whole grains for refined grains in a 6-wk randomized trial favorably affects energy-balance metrics in healthy men and postmenopausal women. Am J Clin Nutr. 2017 Mar;105(3):589-599. doi: 10.3945/ajcn.116.139683. Epub 2017 Feb 8.