Table 1.
Studies on the effects of VLCDs on gut microbiota.
| AUTHOR, YEAR | TYPE OF STUDY | TYPE OF DIET | SAMPLE | DURATION | FINDINGS |
|---|---|---|---|---|---|
| Simoes, 2014 (18) | Randomized trial | VLCD (VLED) | 16 obese patients | 12 months | Changes in fecal microbial numbers in obese individuals were primarily affected by dietary intake rather than by weight change. Bifidobacteria and Lactobacillus decreased after the VLED, but the change was transient. |
| 800 kcal, CHO 67 g, PROT 90 g, FAT 9.5 g | |||||
| Sandrine, 2016 (19) | Randomized trial | VLCKD (VLCD) | 16 obese patients | 52 weeks | Reduction in the Bacteroidetes : Firmicutes ratio was related to metabolic syndrome rather than BMI. VLCD was associated with a reduction in Roseburia and an increase in Akkermansia. Bifidobacteria numbers did not fall, possibly due to the presence of inulin. |
| (800 Kcal, CH0 <30%) | |||||
| Basciani, 2020 (20) | Randomized controlled trial | VLCKD (VLCD) | 48 obese patients | 45 days | After diet, the relative abundance of Firmicutes was significantly decreased while Bacteroidetes increased proportionally with the only exception in the VPG in which the increase in Bacteroidetes not reached statistical significance suggesting that the origin of proteins may influence the microbiota change |
| 90 g protein | divided in three group: 1- WPG 2- VPG APG | ||||
| 26 g carbohydrates | |||||
| 15 g lipids | |||||
| Aleman, 2018 (21) | Prospective cohort study | VLCKD (VLCD) | 1- 10 obese postmenopausal women | 46 days | Roseburia decreased and Christensenellenaceae increased after VLCKD. No significant changes were observed in the Bacteroidetes : Firmicutes ratio. During ketosis, β-hydroxybutyrate production was negatively correlated with F. prausnitzii and Roseburia contrasting with the results of other studies cited above. The question remains to be explored. |
| 54% PROT | |||||
| 26% CHO | |||||
| 20% FAT | |||||
| Carolina Guitérrez-Repiso, 2021 (22) | Controlled parallel design trial | VLCKD (VLCD) | 61 obese patients divided in three group: | 2 months | In this study, as in other previous ones, in patients who underwent VLCKD there was a significant increase in Alistipes (Rikenellaceae family) while a decrease in Lactobacillus was recorded. There was also a decrease in Orodibacter splanchnicus (which in the previous study by the same author only increased if it was accompanied by probiotic supplementation) and there was an increase of Parabacteroides. |
| Guitérrez-Repiso, 2019 (23) | Randomized, single blind, parallel-design | VLCKD (VLCD) | 33 obese patients divided in three group: 2- synbiotics1-sunbiotc2, 3- placebo-synbiotic2, control. |
2 months (VLCKD) + 2 months (LCD) | The authors verify that the VLCKD program not alter the gut microbial population and that the Bacteroidetes/Firmicutes ratio correlates significantly with the percentage of weight loss. In particular, it is evident, in the placebo/synbiotc2 group, that the administration of probiotics such as Bifidobacterium animal subps lactis and prebiotic fibers was able to increase the weight gain (compared to the control) also decreasing the inflammatory state. |
| 75 g protein | |||||
| 20 g carbohydrates | |||||
| 3 g fat |
BMI, body mass index; CHO, carbohydrates; VLCD, very low calorie diet; VLCKD, very low calorie ketogenic diet; VLED, very low energy diet; PROT, proteins; WPG, diet with whey protein group; VPG, diet with vegetable protein group; APG, diet with animal protein group; MetDiet, Mediterranean Diet, BS, Bariatric Surgery.