The impact of weight cycling on gut microbiome richness and diversity in female rats

Female Fischer 344 rats were divided into control (access to food ad libitum) and weight cycling (60% diet restriction followed by ad libitum refeeding) groups. The weight cycles consisted of two weeks dietary restriction and three weeks refeeding for three cycles. Fecal microbiome samples were collected following the initial dietary restriction, the initial refeeding, and the final refeeding periods (and corresponding times in control rats). We observed significant differences in alpha diversity between fecal microbiomes following the initial dietary restriction and the final refeeding period. We additionally observed a significant recovery of alpha diversity following the first refeeding period that we did not observe following the third refeeding in the weight cycling group. Differences in relative abundances of taxa included a higher relative abundance of Bacillota (synonym Firmicutes) in the weight cycling group. Species richness of the weight cycling fecal microbiomes significantly decreased across the study period. Inguinal fat tissue was significantly lower in the weight cycling than ad libitum group, yet heart weight and postprandial HOMA‐IR were significantly higher. Together, these results suggest that repeated weight cycling from repeated periods of dietary restriction has adverse effects on host condition and microbial diversity, potentially leading to long‐term negative health outcomes.