Joint Association of Diet Index for Gut Microbiota and MVPA With Central Obesity: The Mediating Role of Biological Age

ABSTRACT This study examined the independent/joint effects of diet‐gut microbiota (DI‐GM) scores and moderate‐to‐vigorous physical activity (MVPA) on central obesity and mediation via biological aging. Using NHANES 2007–2018 data (17,012 adults), DI‐GM scores and MVPA (MET‐minutes/week) were assessed. Central obesity was defined as BMI ≥ 25 + waist‐height ratio ≥ 0.5. Biological age was measured via Klemera Doubal Method (KDM), phenotypic age (PA), and homeostasis disorder (HD). Multivariable logistic regression and mediation analyses evaluated associations. Each 1‐point DI‐GM increase reduced central obesity prevalence by 9% (OR = 0.91, 95% CI, 0.89%–0.94%, p < 0.001). Meeting MVPA recommendations (≥ 600 MET‐min/week) lowered prevalence by 18% (OR = 0.82, 0.71%–0.94%, p < 0.001). Participants with DI‐GM ≥ 6 + adequate MVPA had maximal risk reduction (OR = 0.60 vs. DI‐GM ≤ 4 + inadequate MVPA, 0.49%–0.75%, p < 0.001). Biological aging mediated 20.12% (KDM), 22.63% (PA), and 1.68% (HD) of DI‐GM's protective effects ( p < 0.05), but not MVPA's effects. Stronger associations occurred in females, college‐educated individuals, and those with 7–8 h sleep ( p ‐interaction < 0.05). Higher DI‐GM scores and adequate MVPA significantly reduced central obesity prevalence, partially mediated by slower biological aging. Integrating gut microbiota‐targeted diets with physical activity may enhance obesity prevention.