EXHIBIT 32.1

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002



In connection with the Quarterly Report of Medifast, Inc. (the "Company") on
Form 10-Q for the quarter ended March 31, 2005 as filed with the Securities and
Exchange Commission on the date hereof (the "Report"), I Bradley T. MacDonald,
Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. Section
1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, to
the best of my knowledge, that:

      (1)   The Report fully complies with the requirements of Section 13(a) or
            15(d) of the Securities Exchange Act of 1934, as amended; and

      (2)   The information contained in the report fairly presents, in all
            material respects, the financial condition and results of the
            operations of the Company.



By: /s/ Bradley T. MacDonald
    --------------------------------
    Bradley T. MacDonald
    Chief Financial Officer
    May 10, 2005