Technical Abstract: Objective: Supplementation of chromium as chromium picolinate (CrPic), 200 µg Cr/d, is claimed to promote weight loss and propitiously affect body composition; it may adversely affect iron status. This study tested the hypothesis that supplementation of CrPic, compared to an equivalent amount of picolinic acid (PA) in CrPic and placebo (P), decreases body weight, alters body composition and reduces iron status of women fed diets of constant energy and nutrients. Design: Eighty-three healthy women (19-50 y) received nutritionally balanced diets composed of Western foods for 12 wk in a double blind, randomized controlled trial. The diets contained 29±5 µg Cr/d by analysis. During an initial 2-wk period, food intake needed to establish individual energy needs to maintain body weight was determined. The women were matched by body mass index and transferrin and randomized to receive supplements containing 200 µg of Cr+3 as CrPic (n=27), 1720 µg of PA (n=27), or P (n=29) for 12 wk. They resided in their homes and maintained their usual activity levels. Body composition was determined and fasting venous blood was analyzed for Cr and iron; timed 24-hr urine samples were analyzed for Cr. Results: CrPic supplementation increased (p<0.0001) serum Cr concentration and urinary Cr excretion compared to PA and P. CrPic did not affect body weight or fat, although all groups lost (p<0.05) weight and fat; it did not affect fat-free, mineral free mass or measures of iron status. Conclusion: Under conditions of controlled energy intake, CrPic supplementation of women did not independently influence body weight or composition or iron status. Thus, claims that supplementation of 200 µg Cr as CrPic promotes weight loss and body composition changes are not supported.