Caloric restriction disrupts the microbiota and colonization resistance.

Diet is a major factor that shapes the gut microbiome1, but the consequences of diet-induced changes in the microbiome for host pathophysiology remain poorly understood. We conducted a randomized human intervention study using a very-low-calorie diet (NCT01105143). Although metabolic health was improved, severe calorie restriction led to a decrease in bacterial abundance and restructuring of the gut microbiome. Transplantation of post-diet microbiota to mice decreased their body weight and adiposity relative to mice that received pre-diet microbiota. Weight loss was associated with impaired nutrient absorption and enrichment in Clostridioides difficile, which was consistent with a decrease in bile acids and was sufficient to replicate metabolic phenotypes in mice in a toxin-dependent manner. These results emphasize the importance of diet-microbiome interactions in modulating host energy balance and the need to understand the role of diet in the interplay between pathogenic and beneficial symbionts.

Thrifty energy phenotype predicts weight regain in postmenopausal women with overweight or obesity and is related to FGFR1 signaling.

BACKGROUND&AIMS: Long term improvement of body weight and metabolism is highly requested in obesity. The specific impact of weight loss associated temporary negative energy balance or modified body composition on metabolism and weight regain is unclear. METHODS: We randomly assigned 80 post-menopausal women (BMI 33.9 (32.2-36.8)kg/m2) to an intervention (IG) or control group (CG). IG underwent a dietary three month-weight loss intervention followed by a four week-weight maintenance period without negative energy balance. The CG was instructed to keep their weight stable. Phenotyping was performed at baseline (M0), after weight loss (M3), the maintenance period (M4) and 24-month follow-up (M24). Co-primary outcomes were changes of insulin sensitivity (ISIClamp) and lean body mass (LBM). Energy metabolism and adipose gene expression were secondary endpoints. RESULTS: Between March 2012 and July 2015, 479 subjects were screened for eligibility. 80 subjects were randomly assigned to IG (n = 40) or CG (n = 40). The total number of dropouts was 18 (IG: n = 13, CG: n = 5). LBM and ISIClamp were stable in the CG between M0 and M3, but were changed in the IG at M3 (LBM: -1.4 (95%CI -2.2-(-0.6)) kg and ISIClamp: +0.020 (95%CI 0.012-0.028) mg·kg-1·min-1/(mU·l-1)) (p < 0.01 and p < 0.05 for IG vs. CG, respectively). Effects on LBM, ISIClamp, FM and BMI were preserved until M4. Lower resting energy expenditure per LBM (REELBM) at M3 and stronger difference of REELBM between M3 and M4 (ΔREELBM-M3M4), which indicates a thrifty phenotype, were positively associated with FM regain at M24 (p = 0.022 and p = 0.044, respectively). Gene set enrichment analysis revealed a relationship of this phenotype to weight loss-induced adaption of adipose FGFR1 signaling. CONCLUSION: Negative energy balance had no additional effect on insulin sensitivity. FGFR1 signaling might be involved in the adaption of energy expenditure to temporary negative energy balance, which indicates a thrifty phenotype susceptible to weight regain. TRIAL REGISTRATION: ClinicalTrials.gov number: NCT01105143, https://clinicaltrials.gov/ct2/show/NCT01105143, date of registration: April 16th, 2010.