Overconsumption of energy-rich food is a major contributor to the obesity epidemic, and has been shown to alter the gut microbiome across species. We previously showed alterations in gut microbiota in the rat in response to chow-based high fat diet at the species level (Lecomte et al, 2015). Further we demonstrated that changes in species abundance were correlated with the deterioration of metabolic parameters associated with obesity. Here we used a 16S rRNA high throughput sequencing to compare the faecal microbiota of rats either continuously fed chow or palatable cafeteria diet that included western foods to a ‘cycled’ group switched between the two diets (chow for 4, cafeteria for 3 days/week). DNA was extracted from faecal samples [chow (n=10), cafeteria (n=11), and cycled (n=11)]. Microbial composition was assessed by high-throughput sequencing of 16S rRNA using Tag-encoded FLX amplicon pyrosequencing (28F, average read length: 400 bp) based upon established protocols.
Cycled rats showed large excursions in food intake, consuming 30% more energy than those maintained on cafeteria diet when switched to this diet, but half as much as those maintained on chow when switched to chow (P<0.01). At 16 weeks, metabolic parameters of cycled rats were intermediate between those of the other diet groups (P<0.05). The total number of species and species richness dropped significantly with cafeteria diet (Number of species: Chow: 365±66, Caf: 285±32, Cycl: 293±20; Richness: Chow: 79±14, Caf: 62±7, Cyc: 63±4). Thus overall microbiota of cycled rats was nearly indistinguishable from rats under constant cafeteria diet, and both these groups were significantly different to the chow group. Our findings indicate that intermittent exposure to cafeteria diet (3 days/week) is sufficient to shift the gut microbiota towards an obese phenotype. These findings may have particular relevance to people who repeatedly switch between healthy and junk foods.