Exploring the gut microbiota alterations with obesity in older adults: a case-control study in the context of Bushehr...

Obesity among older adults presents a serious public health challenge worldwide. The gut microbiota plays a key role in metabolic health and obesity, however its specific alterations in older adults with obesity remain unclear. This study aimed to assess the differences in the abundance of certain indicator gut bacterial genera between older adults with obesity and those with normal weight.

We conducted a case-control study in 2025 involving 104 individuals with obesity and 185 with normal weight, selected from the participants in phase III of the Bushehr Elderly Health (BEH) Program. The obesity group included individuals with a body mass index (BMI) ≥ 30 kg/m² along with waist circumference > 88 cm for women or > 102 cm for men, while the normal weight group had BMI between 18.5 and 24.9 kg/m² and waist circumference below these thresholds. Quantitative real-time PCR was used to measure the abundance of six indicator gut bacterial genera. Statistical analyses, including multiple logistic regression, were employed to evaluate associations between bacterial genera abundance and obesity status, with confounders identified by Directed Acyclic Graph.

The participants' mean age was 72.78 ± 3.08 years. In the obesity and normal weight groups, 38.5% and 67.6% of participants were male, respectively. The abundance of Bacteroides (odds ratio [OR]: 0.681, 95% CI: 0.535-0.866), Blautia (OR: 0.450, 95% CI: 0.301-0.673) and Faecalibacterium (OR: 0.750, 95% CI: 0.583-0.965) were negatively associated with obesity in older adults, after adjusting for age, sex, socioeconomic status, physical activity, and nutritional status.

This study highlights the association between specific gut microbiota and obesity in older adults. Understanding this association and interventions targeting the indicator bacteria may contribute to healthy aging by mitigating obesity and its related metabolic disorders.