Exploring the gut microbiota alterations with obesity in older adults: a case-control study in the context of Bushehr Elderly Health (BEH) program.

Bacteroides abundance was negatively associated with obesity in older adults.

• Odds ratio of 0.681 (95% CI: 0.535–0.866) after adjusting for confounders.
• Confounders adjusted for included age, sex, socioeconomic status, physical activity, and nutritional status.
• Confounders were identified using a Directed Acyclic Graph.
• Quantitative real-time PCR was used to measure bacterial abundance.

Blautia abundance was negatively associated with obesity in older adults.

• Odds ratio of 0.450 (95% CI: 0.301–0.673) after adjusting for confounders.
• This was the strongest inverse association observed among the three significant genera.
• The study included 104 individuals with obesity and 185 with normal weight.
• Confounders adjusted for included age, sex, socioeconomic status, physical activity, and nutritional status.

Faecalibacterium abundance was negatively associated with obesity in older adults.

• Odds ratio of 0.750 (95% CI: 0.583–0.965) after adjusting for confounders.
• Confounders adjusted for included age, sex, socioeconomic status, physical activity, and nutritional status.
• Six indicator gut bacterial genera were measured in total using quantitative real-time PCR.

The study population consisted of older adults with a mean age of approximately 72.78 years, with sex distribution differing between obesity and normal weight groups.

• Participants' mean age was 72.78 ± 3.08 years.
• In the obesity group, 38.5% of participants were male, compared to 67.6% in the normal weight group.
• The study was a case-control design conducted in 2025 using participants from phase III of the Bushehr Elderly Health (BEH) Program.
• The obesity group was defined by BMI ≥ 30 kg/m² plus waist circumference > 88 cm for women or > 102 cm for men; the normal weight group had BMI between 18.5 and 24.9 kg/m² with waist circumference below these thresholds.

Multiple logistic regression with DAG-identified confounders was used to evaluate associations between bacterial genera abundance and obesity status.

• Confounders were identified by Directed Acyclic Graph (DAG).
• Confounders included age, sex, socioeconomic status, physical activity, and nutritional status.
• Six indicator gut bacterial genera were quantified using quantitative real-time PCR.
• The case-control study included a total of 289 participants (104 cases, 185 controls).