(P30-051-24) Study Protocol: A Randomized, Controlled, Crossover Feeding Trial Assessing the Effects of a High-Fiber Cereal on the Metabolizable Energy of the Diet

Objectives: Dietary fiber intake is associated with a lower risk of weight gain and incidence of overweight and obesity. Certain dietary fibers can reduce fat and protein digestibility, reducing dietary metabolizable energy content. Fiber also affects the gut microbiota, contributing to energy balance through direct and indirect mechanisms. Our primary objective was to evaluate the metabolizable energy of the diet with and without the inclusion of a high-fiber blend cereal. Secondary objectives included evaluating the effects of the high-fiber blend cereal on the gut microbiota. We hypothesized that including a high-fiber cereal would reduce the metabolizable energy of the diet.

Methods: Healthy adults (n=19; age 22–75 y, BMI 18.5–39.9 kg/m², and fasting glucose < 126 mg/dL) were recruited to participate in a double-blind, randomized, controlled, crossover study with two experimental conditions (2 weeks each) separated by a 2-week washout. The study was a fully controlled feeding intervention with the same base diet consumed in each experimental condition; the base diet was supplemented with either three servings/day (282 total kcal) of a low (1g) or high (30 g) fiber cereal. Diets were scaled according to energy requirements such that participants remained weight stable. After a 9-day acclimation period, participants collected all urine and fecal samples produced over five days (as marked by a Brilliant Blue fecal collection marker). Combustible energy, protein, fat, and total dietary fiber were measured in composite samples of the diet and feces; urine was analyzed for combustible energy and nitrogen. Metabolizable energy and apparent digestibility coefficients were calculated. Participants completed daily compliance logs and gastrointestinal symptom and bowel habit questionnaires during both conditions. Fecal microbiota sequence data (V4 region, 16S rDNA gene) were analyzed using DADA2 and QIIME2.

Results: N/A

Conclusions: We anticipate that daily consumption of high-fiber cereal will decrease the metabolizable energy of the diet and affect the fecal microbiota.

Funding Sources: The Bell Institute of Health and Nutrition, General Mills Inc.