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 Annual Report of Medifast, Inc. (the “Company”) on Form 10-Q for the quarter ended March 31, 2007, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I Bradley T. MacDonald, Chief Executive Officer of the Company and I Michael S. McDevitt, Chief Financial Officer, 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/ Michael S. McDevitt

Michael S. McDevitt

Chief Executive Officer, Chief Financial Officer

May 10, 2007