Metabolic phenotypes and the gut microbiota in response to dietary resistant starch type 2 in normal-weight subjects: a randomized crossover trialOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This randomized, double-blind, crossover trial tested whether resistant starch type 2 (RS2) affects body fat, glucose metabolism, gut hormones, and the gut microbiota in people of normal weight. Participants took 40 grams per day of high-amylose RS2 or an energy-matched control starch. Each starch was given for four weeks with a four-week washout. All subjects ate an identical controlled diet. Abdominal fat was measured by MRI, and microbiota was profiled by 16S rRNA sequencing.
Who was studied?
The trial enrolled 19 Chinese adults of normal weight (10 women and 9 men) who completed the crossover, from 22 screened. Eligible subjects were aged 18 to 55 years with a body mass index below 24. All were healthy human volunteers recruited in Shanghai, China. Microbiota analysis used data from 17 participants after excluding contaminated samples. The controlled uniform diet was designed to remove interference from dietary components like fat and tea polyphenols.
What were the most important findings?
Resistant starch significantly reduced the visceral fat area (27.05 versus 21.70 cm2, p < 0.001) and the subcutaneous fat area, without changing total body weight. LDL cholesterol, blood urea nitrogen, and uric acid also fell. At 30 minutes after a meal, insulin, C-peptide, and active GLP-1 rose after RS intake. Serum acetate increased (about 53 versus 39 micromolar, p < 0.001) and correlated with the GLP-1 rise. Among microbes, Ruminococcaceae UCG-005 increased while genera including Akkermansia, Ruminococcus 2, Victivallis, and Comamonas shifted. Fifteen genera decreased after RS.
What are the greatest implications of this study?
The trial provides human evidence that a daily 40-gram dose of resistant starch type 2 can lower abdominal fat and improve early-phase hormone secretion in normal-weight people, with no reported adverse events. It suggests fat-specific MRI, not body weight alone, is needed to detect these effects. Baseline abundance of certain taxa predicted the hormonal and fat responses, hinting that microbiota may mediate the benefit. The sample was small, so larger and mechanistic studies are warranted.