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 September 30, 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
        November 9, 2005


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