TABLE 2.

Summary of the animal studies investigating the effects of fasting on gut microbiota.

Study	Dietary restriction regimen	Study model	Gut microbiota variations induced by dietary restrictions	Potential health benefits	Microbiota analyzing methods
Shi et al. (21)	IF for 4 days in two cycles	Hypertensive rat	Lactobacillus and Bifidobacterium abundance increased in the IF group than control.	Rats in the IF group had significantly lower blood pressure than control group.	Shotgun sequence analysis of the microbiota and untargeted metabolomics
Zhang et al. (42)	(1) Fed ad libitum, (2) 30% CR, (3) 5:2 IF regimen	7-week-old C57BL/6 male mice	30% CR led to a significant increase in the Lactobacillus, and significant reduction in the Bacteroidetes. 5:2 IF regimen led to increase in the Bacteroides, Alloprevotella and significant reduction in the Lactobacillus.	IF group consume more energy than ad libitum and CR groups in the first 4 days after refeeding. Both of the CR and IF group had lower body weights, white adipose tissue and serum cholesterol than ad libitum group.	16S rRNA gene sequencing
Liu et al. (14)	Four groups: control (C), intermittent fasting (F), melatonin (M), and intermittent fasting plus melatonin (MF)	Male C57BL/6J mice	The F and M groups had significantly lower alpha diversity than the MF group. Increase in the abundance of Lactobacillus, Ruminococcus, and Akkermansia in the F group than control group. Reduction in the abundance of Helicobacter, Prevotella, and Parasutterella in the F group than C group.	There was no difference between the groups in the cumulative food intake. IF group had lower body weight, serum glucose and TG than control or melatonin groups.	16S rRNA gene v3–v4 amplicon
Deng et al. (23)	Ad libitum (AL) group or an IF group for 30 days	Male C57BL/6J mice	IF did not change the bacterial community richness Reduction in the Firmicutes to Bacteroidetes (F/B ratio) and relative increase in the Allobaculum abundance.	Weight was significantly reduced in the fasting group, but the cumulative energy intake was not different. IF reduced liver steatosis and lipid metabolisme.	16S rDNA gene amplicon sequencing
Li et al. (28)	Ad libitum control group or intermittent fasting groups.	C57BL/6JLvri mice	There were not significant differences between two groups in alpha diversity Mice in the 16 h fasting had increased level of Akkermansia and decreased level of Alistipes.	Cumulative food intake was not changed in the 12 h fasting but changed in the 16 and 20 h fasting.	16S rRNA gene amplicon sequencing
Park et al. (43)	IF vs. ketogenic diet	Male Sprague Dawley rats: Alzheimer’s disease (AD) model	In the IF group than keto group: Clostridiales abundance decrease and Lactobacillales increase.	IF than keto improved memory function.	16S rRNA amplicon sequencing
Kim et al., (44)	Fasting: the ruminal fluids feeding and 24 h after fasting	Three ruminally cannulated Holstein steers	Reduced abundance of Anaerovibrio lipolytica, Eubacterium ruminantium, Prevotella albensis, Prevotella ruminicola, and Ruminobacter amylophilus.	Increase in the gas, ammonia, and microbial protein production.	Denaturing gradient gel electrophoresis and quantitative polymerase chain react
Cignarella et al. (22)	In the IF mice, food pellets were provided or removed at 9 a.m. each day. Control group had unrestricted access to food	Mice	Lactobacillaceae, Bacteroidaceae, and Prevotellaceae families increased in the IF group. Fecal transplantation from mice in IF group to control, reduced the severity of EAE in this group.	IF reduced the differentiation of native T cells into T17 cells.	16S rRNA gene sequencing
Catterson et al. (45)	A 40-day course includes 2-day fed and 5 fasting days	Fruit flies (Drosophila melanogaster)	Reduced bacterial abundance in IF group than control Reduction in age-related pathologies and improved gut barrier function in the IF group.	Increases Stress Resistance, not changed cumulative food intake.	qPCR quantification of bacterial load
Beli et al. (12)	Ad libitum diet vs. intermittent fasting ad libitum diet as 24 h feeding-24 h fasting	db/db mice	Increased levels of Firmicutes and decreased Bacteroidetes and Verrucomicrobia in intermittent fasting group.	Glycated hemoglobin levels were not affected by the IF regimen, survival rate was significantly improved in the IF group.	16S rRNA sequencing with the MiSeq platform
Wei et al., (46)	Fasting diet with 30% restriction of calorie for 1 week	6-week-old male C57BL/ksJ-db	Increase in the Lactobacillaceae, Bacterioidaceae, and Prevotellaceae abundance.	Increase in the ketone production Decrease in the proinflammatory cytokines.	16 s rRNA sequencing
Bahl et al. (15)	3 days of food deprivation (fasting)	Farmed mink (Neovision vision)	The bacterial load and community structure within the mucus was not severely impacted by 3 days of fasting.	–	16S rRNA gene sequencing
McCue et al. (47)	21 days of fasting	Mice, quail, tilapia, toad, geckos	Alteration in Bacteriodetes, Firmicutes, Proteobacteria, Fusobacteria, and Verrucomicrobia.	Changes in distal intestine morphology.	16S rRNA sequencing
Sonoyama et al. (48)	96 h fasting compared to the control group	Male Syrian hamsters	Increase in the proportions of injured bacterial Cells Increase Akkermansia muciniphila, a mucin degrader, in fasting group Clostridia increased in the fed group	Reduction of total SCFA concentration in the fasted group than fed group.	16S rRNA clone library and species specific real-time quantitative PCR

AD, Alzheimer’s disease; CR, calorie restriction; IF, Intermediate fasting; SCFA: short chain fatty acid.