Background: We hypothesized that favorable changes in dietary patterns would lead to a reduction in body size and an improvement in metabolic status. Objective: The objective was to study changes in diet patterns relative to changes in body size, blood pressure, and circulating concentrations of lipids, glucose, insulin, adiponectin, and other cytokines in the context of a 1-y randomized intervention study. Design: For 1 y, 187 men aged 45 ± 2y, ≈50% of whom met the criteria of the metabolic syndrome, were randomly assigned to a diet protocol (n = 45), an exercise protocol (n = 48), a protocol of diet plus exercise (n = 58), or a control protocol (n = 36). A previously defined a priori diet score was created by summing tertile rankings of 35 food group variables; a higher score generally reflected recommended dietary changes in the trial (mean ± SD at baseline: 31 ± 6.5; range: 15-47). Results: Over the study year, the diet score increased by ≈2 ± 5.5 in both diet groups, with a decrease of an equivalent amount in the exercise and control groups. The weight change was -3.5 ± 0.6 kg/10-point change in diet score (P < 0.0001), similarly within each intervention group, independently of the change in energy intake or baseline age and smoking status. Weight change was attenuated but remained significant after adjustment for intervention group and percentage body fat. Subjects with an increased diet score had more favorable changes in other body size variables, systolic blood pressure, and blood lipid, glucose, insulin, and adiponectin concentrations. Change in diet score was unrelated to resistin and several cytokines. Conclusion: The change toward a more favorable diet pattern was associated with improved body size and metabolic profile.