Green Tea Catechin Plus Inulin Improves Insulin Resistance Without Reducing Visceral Fat and Shows Exploratory Gut Microbiota Signals in Adults with Visceral Obesity: A Double-Blind Randomized Controlled Trial.

The 12-week change in visceral fat area (VFA) did not differ significantly between the catechin + inulin group and the placebo group.

• Primary outcome was change in VFA measured by bioelectrical impedance.
• Mean change in VFA: +0.91 cm2 in the catechin + inulin group vs. +4.61 cm2 in the placebo group.
• Between-group difference was not statistically significant (p = 0.243).
• Full analysis set included 47 participants in the catechin + inulin group and 44 in the placebo group.

HOMA-IR decreased in the catechin + inulin group and increased in the placebo group, yielding a significant between-group difference.

• Mean change in HOMA-IR: -0.32 in the catechin + inulin group vs. +0.18 in the placebo group.
• Between-group difference was statistically significant (p = 0.020).
• HOMA-IR was a secondary outcome of the trial.
• The intervention consisted of catechins 400 mg/day plus inulin 2.3 g/day delivered as a beverage over 12 weeks.

No other secondary outcomes showed significant between-group differences.

• Secondary outcomes included metabolic markers and liver fat assessed by the controlled attenuation parameter (CAP).
• None of the other secondary outcomes reached statistical significance between groups.
• The trial was conducted in Japanese adults aged 20–75 years with visceral fat area ≥ 80 cm2 and BMI ≥ 23 kg/m2.

In exploratory gut microbiota analyses, Coprococcus and Bifidobacterium showed nominal between-group differences, but no genus remained significant after false discovery rate (FDR) correction.

• Analyses were conducted at the genus level.
• Coprococcus and Bifidobacterium had unadjusted p < 0.05 for between-group differences.
• No genus remained statistically significant after FDR correction.
• These microbiota findings are characterized as exploratory.

Changes in Coprococcus abundance were inversely correlated with changes in HOMA-IR.

• Pearson correlation coefficient r = -0.28 between changes in Coprococcus and changes in HOMA-IR.
• This correlation was statistically significant (p = 0.010).
• The inverse correlation suggests that increases in Coprococcus were associated with decreases in insulin resistance.
• This finding is described as exploratory and the authors state it warrants further investigation.

The trial was a double-blind, parallel-group, randomized, placebo-controlled design enrolling 96 participants.

• 96 participants were randomized: catechin + inulin group n = 49, placebo group n = 47.
• Participants were Japanese adults aged 20–75 years with VFA ≥ 80 cm2 and BMI ≥ 23 kg/m2.
• Intervention duration was 12 weeks.
• The trial was registered in the Japan Registry of Clinical Trials (jRCTs021230004, registered 16 May 2023).
• The active beverage contained catechins 400 mg/day and inulin 2.3 g/day.