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Gut bacteria may provide clues to diet success

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September 26, 2017

Mads Fiil Hjorth
Mads F. Hjorth

Adults with overweight or obesity determined to have a high ratio of two microbial enterotypes saw greater body fat loss after an intervention with a high-fiber diet compared with those who had a low ratio, according to findings reported in the International Journal of Obesity.

“Clustering of the human gut microbiota, designated enterotypes, was first described in 2011,” Mads F. Hjorth, PhD, assistant professor in the department of nutrition, exercise and sports at the University of Copenhagen, Denmark, and colleagues wrote. “The Bacteroides-driven enterotype is reported to be predominant in individuals consuming more protein and animal fat (Western diet), whereas the Prevotella-driven enterotype appears predominant in subjects consuming more carbohydrate and fiber.”

As a proxy for enterotypes, Hjorth and colleagues studied pretreatment Prevotella to Bacteroides ratio as a prognostic marker for successful body fat loss after two diets with differing fiber and whole grain content. The researchers analyzed data from 181 participants with overweight or obesity randomly assigned to an ad libitum new Nordic diet (high in dietary fiber, whole grains, fruit and vegetables) or a control diet designed to match the macronutrient composition of the typical Danish diet for 26 weeks. All food and drink were supplied for the study. Participants provided fasting blood samples at baseline; waist circumference and fat mass via DXA were measured at randomization and 12 and 26 weeks; 62 participants provided fecal samples at baseline to assess Prevotella to Bacteroides ratio. Participants were stratified as having a high Prevotella to Bacteroides ratio (mean age, 42 years; 64.3% women; mean BMI, 31 kg/m²) or a low Prevotella to Bacteroides ratio (mean age, 48 years; 69.2% women; mean BMI, 29 kg/m²).

At week 26, participants with a high Prevotella to Bacteroides ratio experienced an average 3.15 kg greater body fat loss on the new Nordic diet vs. those with a high Prevotella to Bacteroides ratio on the control diet (95% CI, 1.55-4.76). However, there were no between-diet differences among participants with a low Prevotella to Bacteroides ratio. Additionally, among those assigned to the new Nordic diet, those with a high Prevotella to Bacteroides ratio saw a mean 2.27-kg greater body fat loss vs. those with a low Prevotella to Bacteroides ratio (95% CI, 0.09-4.45). Researchers observed similar differences in responses to the diets when assessing waist circumference (P = .032) and body weight (P = .065).

During a 1-year follow-up period, all participants were asked to switch to the new Nordic diet (without food supplied) to investigate the diet in a real-life setting, with weight measured at 52 and 78 weeks. During this follow-up, those with a high Prevotella to Bacteroides ratio changing from control diet to new Nordic diet maintained their weight, whereas those with a low Prevotella to Bacteroides ratio changing from control diet to new Nordic diet regained a mean 2.76 kg, according to researchers.

“Overweight and obese participants with a high [Prevotella to Bacteroides] ratio appeared more responsive to fiber and whole grain than individuals with low [Prevotella to Bacteroides] ratio,” the researchers wrote. “This was further supported by similar findings for waist circumference and body weight.”

The researchers suggested that mechanisms involved could be the efficacy of energy harvest from different foods, differences in fiber-utilization capacity, gut-brain signaling of behavior and the secretion of gastrointestinal hormones affecting appetite.

“We already have analyses from another study that confirmed the finding, and the results are, therefore, robust,” Hjorth told Endocrine Today. “We will now see if we can somehow manipulate these bacteria in our gut so we can all have a high Prevotella to Bacteroides ratio.” – by Regina Schaffer

Disclosures: Gelesis Inc. funded this study. Hjorth and two other authors report they are co-inventors on a pending provisional patent application on the use of biomarkers for the prediction of weight-loss responses.

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