Table 1.
Effects of interventions with dietary fibre, carbohydrates and protein and changes in dietary patterns on gut microbiota and host metabolism in healthy, overweight, obese and insulin resistant individuals
| Diet | Study design | Functional outcomes | Gut microbiota composition and functionality | Individuals | Reference |
| Dietary protein | |||||
| High protein/moderate CHO (HPMC) and HP/low CHO (HPLC) | 28-day, randomised, cross-over design | HPMC and HPLC: increased faecal branched-chain fatty acids and concentrations of phenylacetic acid and N-nitroso compounds | HPMC: no significant changes HPLC: ↓ Roseburia, Eubacterium rectale, Bacteroides spp; no changes in Faecalibacterium prausnitzii |
17 men with obesity (BMI: 30.0–48.5 kg/m2) | 89 |
| LC/higher protein isocaloric | 14 weeks, parallel design | Liver fat ↓ Hepatic lipid metabolism↑ Inflammation ↓ |
Rapid microbial alterations: Streptococcus, Lactococcus and Eggerthella↑ Ruminoccocus, Eubacterium, Clostridium and Bifidobacterium↓ |
10 adults with obesity/NAFLD (BMI: 27–40 kg/m2) |
162 |
| Dietary fibre and carbohydrates | |||||
| Barley kernel bread (37.6 g fibre/day) | 3 days, randomised cross-over design (vs white bread reference 9.1 g fibre/day) | Increased plasma GLP-1, PYY, breath H2 excretion, fasting serum SCFAs, improved insulin sensitivity index (p<0.05) | Increased Prevotella/Bacteroides ratio in responders versus non-responders (post hoc analysis) | 39 healthy adults (BMI: 18–28 kg/m2) | 163 164 |
| 16 g oligofructose (8 g two times) per day | 2 weeks, placebo-controlled (16 g dextrin maltose), parallel design | Reduced 2-hour postprandial glucose AUC (p<0.05) Increased plasma GLP-1 and PYY levels and increased breath–hydrogen excretion | Not determined | 10 healthy adults (BMI mean±SD: 21.6±0.99 kg/m2) | 165 |
| 16 g FOS or GOS per day | 2 weeks, cross-over design | Increased fasting glucose | Bifidobacterium ↑, FOS: butyrate-producing Phascolarctobacterium ↑, GOS: Ruminococcus ↓ | 35 healthy adults (BMI <18 kg/m2) |
23 |
| RS versus NSP (resp. 16 g NSP, 25 g RS vs 42 g NSP, 2.5 g RS) |
3 weeks, randomised cross-over design | Inverse relationship gut microbiota diversity–dietary responsiveness | ↑ Ruminococcaceae and ↑ Lachnospiraceae | 14 men with MetS (BMI: 27.9–51.3 kg/m2) | 124 166 |
| 30 g RS (10 g three times) per day | 4 weeks, placebo controlled (20 g digestible starch), two-way crossover | Improved whole-body insulin sensitivity (euglycaemic–hyperinsulinaemic clamp) (p<0.05). | Not determined | 10 healthy adults (BMI: 18.4–32.3 kg/m2 | 167 |
| 16 g inulin/oligofructose mix (8 g two times) per day | 12 weeks, parallel design, placebo controlled (16 g maltodextrin) | Reduced post-OGTT glucose response (7%, p<0.01); no effects on HOMA, fasting glucose and insulin and HbA1c | ↑Bifidobacterium and F. prausnitzii, ↓ Bacteroides intestinalis, B. vulgatus and Propionibacterium | 30 women with obesity (BMI, >30 kg/m2) | 168 |
| 15 g GOS (5 g, three times) per day | 12 weeks, placebo-controlled (isocaloric maltodextrin), parallel design |
No effects on glucose or insulin homeostasis, no increases in fasting SCFA plasma concentrations or faecal SCFAs | Fivefold increase in faecal Bifidobacterium (p=0.009, q=0.144); no effect microbial richness or diversity | 44 adults with prediabetes andoverweight/obesity (BMI: 25–35 kg/m2) | 22 |
| 5.5 g GOS mixture 1×/day | 12 weeks, placebo-controlled (5.5 g maltodextrin), two-way crossover |
Decreased fasting insulin (p<0.01), triglyceride and C reactive protein plasma concentrations | Increased Bifidobacterium (p<0.0001) | 45 adults with overweight/obesity (BMI >25 kg/m2) | 169 |
| Dietary patterns | |||||
| Animal-based diet (very low fibre) versus plant-based diet (high fibre) | 5 days, cross-over design | Altered bile acid metabolism, plant polysaccharide fermentation ↓ |
Alistipes, Bilophila and Bacteroides ↑ Roseburia, E. rectale and Ruminococcus bromii ↓ |
10 healthy, lean and overweight adults (BMI: 19–32 kg/m2) | 103 |
| Mediterranean diet compared with energy-reduced Mediterranean diet and physical activity promotion | 1 year | BMI, fasting glucose, glycated haemoglobin and triglycerides ↓, high-density cholesterol ↑ |
Butyricicoccus, Haemophilus, Ruminiclostridium 5 and E. hallii ↓ | 400 adults with MetS (BMI ≥27 and ≤40 kg/m2) |
113 |
AUC, area under the curve; BMI, body mass index; FOS, fructo-oligosaccharide; GLP-1, glucagon-like peptide 1; GOS, galacto-oligosaccharide; HOMA, homeostasis model assessment; HP, high protein; HPLC, high protein/low carbohydrate (CHO); HPMC, high protein/moderate carbohydrate (CHO); LC, low CHO; MetS, metabolic syndrome; NAFLD, non-alcoholic fatty liver disease; NSP, non-starch polysaccharide; OGTT, oral glucose tolerance test; PYY, peptide YY; RS, resistant starch; SCFA, short-chain fatty acid.