Consumers of multivitamins and other dietary supplements have lower body weight and less body fat than non-consumers of supplements.  Supplement use also appears to have a significantly impact on appetite.

Male supplement users had lower body weight, fat mass, BMI, and greater resting energy expenditure than non-supplement users.  In females, the same results were observed, but not to the statistically significant level. 

Appetite scores were significantly reduced for female multivitamin and mineral users.  The mineral zinc is a known leptingenic, and leptin is a critical appetite signalling mechanism.

PMID: 17977472