The impact of dietary non-digestible carbohydrate on gut microbiota and metabolic markers in overweight volunteers

Background: The composition of diets consumed following a period of weight loss may have a significant impact on satiety and metabolic health. Intake of non-digestible dietary carbohydrates and fiber is likely to induce changes in the composition of gut microbiota and its metabolites.Objective: This study was aimed to test the effects of including a non-digestible carbohydrate in diets to achieve weight maintenance following a period of weight loss in overweight subjects.Design: Nineteen overweight volunteers (BMI 27-42 kg/m2) of both sexes were first given a maintenance (M) diet of 15% protein, 30% fat, 55% carbohydrate for 3 days then a controlled weight loss (WL) diet (30% protein, 30% fat, 40% carbohydrate) for 21 days, followed by weight maintenance diets (20% protein, 30% fat, 50% carbohydrate) containing either resistant starch (RS type 3) or no RS (C) for 10 days in a cross-over design. Satiety and digestive comfort were assessed by questionnaires and responses to a test meal assessed at the end of each dietary period. Circulating hormones, cytokines, lipids and glucose were determined in blood samples. Composition of gut microbiota and concentrations of microbial metabolites were assessed using 16S rRNA-based qPCR, high throughput 16S rRNA sequencing, and GC-MS respectively, in fecal samples. Results: Decreases in BMI, systolic blood pressure, cholesterol and LDL cholesterol during the WL diet were largely maintained with both the C and RS diets. In addition the RS diet significantly increased specific groups of bacteria in fecal samples and decreased the proportion of branched fatty acids among total short chain fatty acids relative to the C and WL diets and fasting blood glucose levels were significantly lower for the RS than the C diet. Satiety hormones (ghrelin, insulin, GIP) changed significantly during the WL diet but did not differ between RS and C diets. No evidence was found for digestive discomfort with any of the diets.Conclusions: The metabolic benefits from weight loss on a high (30%) protein diet were maintained through a subsequent weight maintenance diet with only 20% protein and higher total carbohydrate. Inclusion of resistance starch (RS) in the weight maintenance diet altered gut microbiota composition and resulted in slightly lower fasting glucose compared with the control (C) diet.