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

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%, <i>p</i> < 0.001). Meeting MVPA recommendations (≥ 600 MET-min/week) lowered prevalence by 18% (OR = 0.82, 0.71%-0.94%, <i>p</i> < 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%, <i>p</i> < 0.001). Biological aging mediated 20.12% (KDM), 22.63% (PA), and 1.68% (HD) of DI-GM's protective effects (<i>p</i> < 0.05), but not MVPA's effects. Stronger associations occurred in females, college-educated individuals, and those with 7-8 h sleep (<i>p</i>-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.