-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 WbfOH4pb3LdG32EgO+NS//wGpkn/F7m2wdjnSYefffFMNYjH6JnsCHGuNe4SzLE6
 2vIHC6kob4XH/Ae0nsqtKg==

<SEC-DOCUMENT>0001317987-06-000001.txt : 20060201
<SEC-HEADER>0001317987-06-000001.hdr.sgml : 20060201
<ACCEPTANCE-DATETIME>20060201200619
ACCESSION NUMBER:		0001317987-06-000001
CONFORMED SUBMISSION TYPE:	5
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051231
FILED AS OF DATE:		20060201
DATE AS OF CHANGE:		20060201

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MEDIFAST INC
		CENTRAL INDEX KEY:			0000910329
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS FOOD PREPARATIONS & KINDRED PRODUCTS [2090]
		IRS NUMBER:				133714405
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		11445 CRONHILL DRIVE
		CITY:			OWINGS MILLS
		STATE:			MD
		ZIP:			21117
		BUSINESS PHONE:		7327640619

	MAIL ADDRESS:	
		STREET 1:		11445 CRONHILL DRIVE
		CITY:			OWINGS MILLS
		STATE:			MD
		ZIP:			21117

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HEALTHRITE INC
		DATE OF NAME CHANGE:	19951120

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	XX
		DATE OF NAME CHANGE:	19950619

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	00
		DATE OF NAME CHANGE:	19950619

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			RNI-NV Limited Partnership
		CENTRAL INDEX KEY:			0001317987
		STATE OF INCORPORATION:			NV
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		5
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31573
		FILM NUMBER:		06571292

	BUSINESS ADDRESS:	
		STREET 1:		C/O BRUCE LESLIE, ESQ.
		STREET 2:		530 SOUTH LAS VEGAS BOULEVARD
		CITY:			LAS VEGAS
		STATE:			NV
		ZIP:			89101
		BUSINESS PHONE:		702-650-2828

	MAIL ADDRESS:	
		STREET 1:		C/O BRUCE LESLIE, ESQ.
		STREET 2:		530 SOUTH LAS VEGAS BOULEVARD
		CITY:			LAS VEGAS
		STATE:			NV
		ZIP:			89101
</SEC-HEADER>
<DOCUMENT>
<TYPE>5
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2005-12-31</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000910329</issuerCik>
        <issuerName>MEDIFAST INC</issuerName>
        <issuerTradingSymbol>MED</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001317987</rptOwnerCik>
            <rptOwnerName>RNI-NV Limited Partnership</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BRUCE LESLIE, ESQ.</rptOwnerStreet1>
            <rptOwnerStreet2>530 SOUTH LAS VEGAS BOULEVARD</rptOwnerStreet2>
            <rptOwnerCity>LAS VEGAS</rptOwnerCity>
            <rptOwnerState>NV</rptOwnerState>
            <rptOwnerZipCode>89101</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-12-31</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1088830</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This Form 5 is being filed solely to report the year-end holdings of the Reporting Person.  All transactions completed during 2005 have been reported on Forms 3 and 4.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>By: RNI Nevada LLC, Its General Partner; by The Robert N. Iwamoto Jr. Trust dated Dec. 30, 1988, Its Manager; by Robert N. Iwamoto, Jr., Trustee; Robert N. Iwamoto, Jr.</signatureName>
        <signatureDate>2006-01-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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