Baseline Ferritin and Body Composition as Correlates of Longitudinal Metabolic Changes During an Energy-Restricted Mediterranean-Style Intervention Across Three Overweight Phlogistic-Related Clinical Conditions

Background/Objectives: Chronic inflammation accompanies obesity, but correlations of longitudinal changes during dietary follow-up remain unclear. We described inflammatory profiles and examined associations of baseline ferritin and body composition with changes during a 32-week energy-restricted Mediterranean-style intervention. Methods: This prospective cohort included 190 adults classified as healthy overweight (n = 49), long COVID with overweight (n = 108), or metabolic syndrome (MS) with overweight (n = 33); 61 healthy normal-weight participants without long COVID or metabolic syndrome contributed to baseline comparisons only. The program prescribed a 30% energy deficit using a Mediterranean-style food-exchange system. Anthropometric, biochemical, inflammatory, lifestyle, and hepatic markers were assessed. MANOVA and multivariable regression examined inflammatory profiles and ferritin-change correlates. Results: Participants with overweight/obesity had a less favorable metabolic and inflammatory profile than normal-weight participants. Baseline ferritin was 100.5 (53.5–178.5), 76.0 (34.0–137.0), and 149.5 (102.0–245.0) ng/mL in the healthy overweight, long-COVID, and MS groups, respectively (omnibus p < 0.001). Mean changes were 8.0 ± 36.4, 3.3 ± 32.6, and −22.0 ± 58.8 ng/mL, respectively (omnibus p = 0.039), with the MS group showing greater decreases. Sex and muscle mass were associated with the multivariate inflammatory profile (both p < 0.001). Clinical group, baseline ferritin, muscle-mass change, MEDAS change, and Fatty Liver Index change were associated with ferritin change, although explanatory performance was limited (adjusted R2 = 0.16). Conclusions: Baseline ferritin and body composition were correlates of heterogeneous inflammatory-metabolic profiles and ferritin changes. These hypothesis-generating associations do not establish causal or mechanistic effects and require controlled confirmation with comprehensive iron-status assessment.