<SEC-DOCUMENT>0001628280-25-033184.txt : 20250626
<SEC-HEADER>0001628280-25-033184.hdr.sgml : 20250626
<ACCEPTANCE-DATETIME>20250626190428
ACCESSION NUMBER:		0001628280-25-033184
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250625
FILED AS OF DATE:		20250626
DATE AS OF CHANGE:		20250626

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Thomas Andrea B
		CENTRAL INDEX KEY:			0001779769
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31573
		FILM NUMBER:		251081796

	MAIL ADDRESS:	
		STREET 1:		C/O MEDIFAST, INC.
		STREET 2:		100 INTERNATIONAL DRIVE
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MEDIFAST INC
		CENTRAL INDEX KEY:			0000910329
		STANDARD INDUSTRIAL CLASSIFICATION:	MISCELLANEOUS FOOD PREPARATIONS & KINDRED PRODUCTS [2090]
		ORGANIZATION NAME:           	04 Manufacturing
		EIN:				133714405
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		100 INTERNATIONAL DRIVE
		STREET 2:		18TH FLOOR
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202
		BUSINESS PHONE:		4105818042

	MAIL ADDRESS:	
		STREET 1:		100 INTERNATIONAL DRIVE
		STREET 2:		18TH FLOOR
		CITY:			BALTIMORE
		STATE:			MD
		ZIP:			21202

	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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1750979063.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-06-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001779769</rptOwnerCik>
            <rptOwnerName>Thomas Andrea B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MEDIFAST, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>100 INTERNATIONAL DRIVE</rptOwnerStreet2>
            <rptOwnerCity>BALTIMORE</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>21202</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-06-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11168</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>24017.123</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These restricted stock units were granted under the Medifast, Inc. Director's Deferred Compensation Plan, as Amended and Restated (the &quot;Plan&quot;), in connection with the payment of the reporting person's annual director fees. Each unit represents the right to receive one share of the Issuer's common stock. These shares are granted from the Issuer's Amended and Restated 2012 Share Incentive Plan and will vest in full on June 25, 2026.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jason L. Groves, attorney-in-fact</signatureName>
        <signatureDate>2025-06-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
