Intermittent Fasting Superior to Caloric Restriction for Gastrointestinal Symptoms (June 2024)

Take Home

The trial found that combining intermittent fasting (IF) with protein pacing (P) significantly improved gut microbiome composition and metabolomic profiles compared to continuous caloric restriction (CR). Participants on the IF-P regimen experienced better gut symptomatology, increased abundance of beneficial microbes like Christensenellaceae, and higher levels of metabolites favoring fat oxidation and anti-inflammatory cytokines. These findings suggest that the IF-P regimen is more effective for weight loss, body composition improvement, and gut health than CR.

Background

The gut microbiome significantly influences body weight, composition, and gastrointestinal functioning, making it a critical target for dietary interventions. Previous research has shown the effectiveness of IF and P in weight loss and body composition enhancement, but their combined effects on the gut microbiome were not well understood. This study aimed to fill that gap by comparing these dietary strategies to provide insights into how they modulate gut health and metabolism. The findings are relevant as they highlight the potential of IF-P regimens to offer more pronounced benefits for weight management, body composition, and gut health, informing future precision nutrition recommendations and therapeutic approaches for metabolic disorders.

Methods

In this randomized controlled trial, 41 individuals with overweight or obesity were assigned to either an intermittent fasting with protein pacing (IF-P) regimen or a continuous caloric restriction (CR) diet. Both dietary interventions were matched for total energy intake and expenditure over an eight-week period. The IF-P regimen involved consuming four protein-rich meals per day, evenly spaced every four hours, combined with an extended modified fasting period of 36–60 hours per week, during which participants consumed 350–550 calories per day. In contrast, the CR diet followed a heart-healthy eating plan aligned with current U.S. dietary recommendations, consisting of 41% carbohydrates, 38% fat, and 21% protein. Participants' dietary intake, body weight, body composition, cardiometabolic outcomes, and hunger ratings were monitored throughout the intervention. Gut microbiome composition was assessed using 16S rRNA gene sequencing, and metabolomic profiles were analyzed using plasma samples. Statistical analyses, including two-way factorial mixed model ANOVA and linear-mixed effects models, were used to evaluate changes in gut microbiome diversity, microbial colonization, and metabolomic profiles. The study aimed to compare the effects of the two dietary strategies on weight loss, body composition, and gut microbiome dynamics.

Results

The study revealed significant differences in the effects of intermittent fasting combined with protein pacing (IF-P) and continuous caloric restriction (CR) on gut microbiome and metabolomic profiles. Participants following the IF-P regimen experienced greater improvements in gut symptomatology and more substantial changes in gut microbiome composition compared to those on the CR diet. Specifically, the abundance of beneficial microbes such as Christensenellaceae increased significantly in the IF-P group. Additionally, the IF-P regimen led to higher levels of circulating cytokines and amino acid metabolites that favor fat oxidation and anti-inflammatory responses. The IF-P group also showed a more significant reduction in body weight and fat mass, alongside an increase in fat-free mass percentage.

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