The purpose of this study was to determine the effects of supplementation with a water-soluble cinnamon extract (Cinnulin PF(R)) on body composition and features of the metabolic syndrome. Twenty-two subjects with prediabetes and the metabolic syndrome (mean +/- SD: age, BMI, systolic blood pressure SBP, fasting blood glucose FBG: 46.0 +/- 9.7 y; 33.2 +/- 9.3 kg/m2; 133 +/- 17 mm Hg; 114.3 +/- 11.6 mg/dL) were randomly assigned to supplement their diet with either Cinnulin PF(R) (500 mg/d) or a placebo for 12-weeks. Main outcome measures were changes in FBG, SBP, and body composition measured after 12-weeks of supplementation. The primary statistical analyses consisted of two factor (group x time), repeated-measures ANOVA for between group differences over time. In all analyses, an intent-to-treat approach was used and significance was accepted at P < 0.05. Subjects in the Cinnulin PF(R) group had significant decreases in FBG (-8.4%: 116.3 +/- 12.8 mg/dL pre to 106.5 +/- 20.1 mg/dL post, p < 0.01), SBP (-3.8%: 133 +/- 14 mm Hg pre to 128 +/- 18 mm Hg post, p < 0.001), and increases in lean mass (+1.1%: 53.7 +/- 11.8 kg pre to 54.3 +/- 11.8 kg post, p < 0.002) compared with the placebo group. Additionally, within-group analyses uncovered small, but statistically significant decreases in body fat (-0.7%: 37.9 +/- 9.2% pre to 37.2 +/- 8.9% post, p < 0.02) in the Cinnulin PF(R) group. No significant changes in clinical blood chemistries were observed between groups over time. These data support the efficacy of Cinnulin PF(R) supplementation on reducing FBG and SBP, and improving body composition in men and women with the metabolic syndrome and suggest that this naturally-occurring spice can reduce risk factors associated with diabetes and cardiovascular diseases.